[109]*109Justice Stewart
delivered the opinion of the Court.
The charter of the appellant Democratic Party of the United States (National Party) provides that delegates to its National Convention shall be chosen through procedures in which only Democrats can participate. Consistently with the charter, the National Party’s Delegate Selection Rules provide that only those who are willing to affiliate publicly with the Democratic Party may participate in the process of selecting delegates to the Party’s National Convention. The question on this appeal is whether Wisconsin may successfully insist that its delegates to the Convention be seated, even though those delegates are chosen through a process that includes a binding state preference primary election in which voters do not declare their party affiliation. The Wisconsin Supreme Court held that the National Convention is bound by the Wisconsin primary election results, and cannot refuse to seat the delegates chosen in accord with Wisconsin law. 93 Wis. 2d 473, 287 N. W. 2d 519.
I
Rule 2A of the Democratic Selection Rules for the 1980 National Convention states: “Participation in the delegate selection process in primaries or caucuses shall be restricted to Democratic voters only who publicly declare their party preference and have that preference publicly recorded.” 1 Under [110]*110National Party rules, the “delegate selection process” includes any procedure by which delegates to the Convention are bound to vote for the nomination of particular candidates.2 The election laws of Wisconsin 3 allow non-Democrats— [111]*111including members of other parties and independents — to vote in the Democratic primary without regard to party affiliation and without requiring a public declaration of party preference. The voters in Wisconsin’s “open”4 primary express their [112]*112choice among Presidential candidates for the Democratic Party’s nomination; they do not vote for delegates to the National Convention. Delegates to the National Convention are chosen separately, after the primary, at caucuses of persons who have stated their affiliation with the Party.5 But these delegates, under Wisconsin law, are bound to vote at the National Convention in accord with the results of the open primary election.6 Accordingly, while Wisconsin’s open Presidential preference primary does not itself violate National Party rules,7 the State’s mandate that the results of the primary shall determine the allocation of votes cast by the State’s delegates at the National Convention does.
In May 1979, the Democratic Party of Wisconsin (State Party) submitted to the Compliance Review Commission of the National Party its plan for selecting delegates to the 1980 National Convention. The plan incorporated the provisions of the State’s open primary laws, and, as a result, the Commission disapproved it as violating Rule 2A.8 Since compliance with Rule 2A was a condition of participation at [113]*113the Convention, for which no exception could be made,9 the National Party indicated that Wisconsin delegates who were bound to vote according to the results of the open primary would not be seated.
The State Attorney General then brought an original action in the Wisconsin Supreme Court on behalf of the State. Named as respondents in the suit were the National Party and the Democratic National Committee, who are the appellants in this Court, and the State Party, an appellee here. The State sought a declaration that the Wisconsin delegate selection system was constitutional as applied to the appellants and that the appellants could not lawfully refuse to seat the Wisconsin delegation at the Convention. The State Party responded by agreeing that state law may validly be applied against it and the National Party, and cross-claimed against the National Party, asking the court to order the National Party to recognize the delegates selected in accord with Wisconsin law. The National Party argued that under the First and Fourteenth Amendments it could not be compelled to seat the Wisconsin delegation in violation of Party rules.
The Wisconsin Supreme Court entered a judgment declaring that the State’s system of selecting delegates to the Democratic National Convention is constitutional and binding on the appellants. 93 Wis. 2d 473, 287 N. W. 2d 519. The court assumed that the National Party’s freedom of political association, protected by the First and Fourteenth Amendments, gave it the right to restrict participation in the process of choosing Presidential and Vice Presidential candidates to Democrats. Id., at 511-512, 287 N. W. 2d, at 536. It concluded, however, that the State had not impermissibly impaired that right. The court said that the State’s primary election laws were themselves intended to permit persons to vote only for the candidates of the party they preferred, and [114]*114that, as a practical matter, requiring a public declaration of party affiliation would not prevent persons who are not Democrats from voting in the primary.10 Moreover, the court reasoned that to whatever extent appellants’ constitutional freedom of political association might be burdened by the Wisconsin election laws, the burden was justified by the State’s “compelling . . . interest in maintaining the special feature of its primary . . . which permits private declaration of party preference.” Id., at 521, 287 N. W. 2d, at 541.
The court declared that the votes of the state delegation at the National Convention for Presidential and Vice Presidential candidates must be apportioned and cast as prescribed by Wisconsin law, and that the State’s delegates could not for that reason be disqualified from being seated at the Convention.11 The National Party and the Democratic National Committee then brought this appeal under 28 U. S. C. § 1257 (2).
Wisconsin held its primary on April 1, 1980, in accord with its election laws. Subsequently, the State Party chose delegates to the 1980 Democratic National Convention, in compliance with the order of the Wisconsin Supreme Court and Wis. Stat. §§ 8.12 (3)(b), (3)(c) 5 (1977). This Court noted probable jurisdiction of the appeal on July 2, 1980. 448 U. S. 909. On the same day, the Court stayed the judgment of [115]*115the Wisconsin Supreme Court. On July 20, 1980, the Credentials Committee of the National Convention decided to seat the delegates from Wisconsin, despite this Court’s stay,12 and despite the delegates’ selection in a manner that violated Rule 2A.13
II
Rule 2A can be traced to efforts of the National Party to study and reform its nominating procedures and internal structure after the 1968 Democratic National Convention.14 [116]*116The Convention, the Party’s highest governing authority, directed the Democratic National Committee (DNC) to establish a Commission on Party Structure and Delegate Selection (McGovern/Fraser Commission).
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[109]*109Justice Stewart
delivered the opinion of the Court.
The charter of the appellant Democratic Party of the United States (National Party) provides that delegates to its National Convention shall be chosen through procedures in which only Democrats can participate. Consistently with the charter, the National Party’s Delegate Selection Rules provide that only those who are willing to affiliate publicly with the Democratic Party may participate in the process of selecting delegates to the Party’s National Convention. The question on this appeal is whether Wisconsin may successfully insist that its delegates to the Convention be seated, even though those delegates are chosen through a process that includes a binding state preference primary election in which voters do not declare their party affiliation. The Wisconsin Supreme Court held that the National Convention is bound by the Wisconsin primary election results, and cannot refuse to seat the delegates chosen in accord with Wisconsin law. 93 Wis. 2d 473, 287 N. W. 2d 519.
I
Rule 2A of the Democratic Selection Rules for the 1980 National Convention states: “Participation in the delegate selection process in primaries or caucuses shall be restricted to Democratic voters only who publicly declare their party preference and have that preference publicly recorded.” 1 Under [110]*110National Party rules, the “delegate selection process” includes any procedure by which delegates to the Convention are bound to vote for the nomination of particular candidates.2 The election laws of Wisconsin 3 allow non-Democrats— [111]*111including members of other parties and independents — to vote in the Democratic primary without regard to party affiliation and without requiring a public declaration of party preference. The voters in Wisconsin’s “open”4 primary express their [112]*112choice among Presidential candidates for the Democratic Party’s nomination; they do not vote for delegates to the National Convention. Delegates to the National Convention are chosen separately, after the primary, at caucuses of persons who have stated their affiliation with the Party.5 But these delegates, under Wisconsin law, are bound to vote at the National Convention in accord with the results of the open primary election.6 Accordingly, while Wisconsin’s open Presidential preference primary does not itself violate National Party rules,7 the State’s mandate that the results of the primary shall determine the allocation of votes cast by the State’s delegates at the National Convention does.
In May 1979, the Democratic Party of Wisconsin (State Party) submitted to the Compliance Review Commission of the National Party its plan for selecting delegates to the 1980 National Convention. The plan incorporated the provisions of the State’s open primary laws, and, as a result, the Commission disapproved it as violating Rule 2A.8 Since compliance with Rule 2A was a condition of participation at [113]*113the Convention, for which no exception could be made,9 the National Party indicated that Wisconsin delegates who were bound to vote according to the results of the open primary would not be seated.
The State Attorney General then brought an original action in the Wisconsin Supreme Court on behalf of the State. Named as respondents in the suit were the National Party and the Democratic National Committee, who are the appellants in this Court, and the State Party, an appellee here. The State sought a declaration that the Wisconsin delegate selection system was constitutional as applied to the appellants and that the appellants could not lawfully refuse to seat the Wisconsin delegation at the Convention. The State Party responded by agreeing that state law may validly be applied against it and the National Party, and cross-claimed against the National Party, asking the court to order the National Party to recognize the delegates selected in accord with Wisconsin law. The National Party argued that under the First and Fourteenth Amendments it could not be compelled to seat the Wisconsin delegation in violation of Party rules.
The Wisconsin Supreme Court entered a judgment declaring that the State’s system of selecting delegates to the Democratic National Convention is constitutional and binding on the appellants. 93 Wis. 2d 473, 287 N. W. 2d 519. The court assumed that the National Party’s freedom of political association, protected by the First and Fourteenth Amendments, gave it the right to restrict participation in the process of choosing Presidential and Vice Presidential candidates to Democrats. Id., at 511-512, 287 N. W. 2d, at 536. It concluded, however, that the State had not impermissibly impaired that right. The court said that the State’s primary election laws were themselves intended to permit persons to vote only for the candidates of the party they preferred, and [114]*114that, as a practical matter, requiring a public declaration of party affiliation would not prevent persons who are not Democrats from voting in the primary.10 Moreover, the court reasoned that to whatever extent appellants’ constitutional freedom of political association might be burdened by the Wisconsin election laws, the burden was justified by the State’s “compelling . . . interest in maintaining the special feature of its primary . . . which permits private declaration of party preference.” Id., at 521, 287 N. W. 2d, at 541.
The court declared that the votes of the state delegation at the National Convention for Presidential and Vice Presidential candidates must be apportioned and cast as prescribed by Wisconsin law, and that the State’s delegates could not for that reason be disqualified from being seated at the Convention.11 The National Party and the Democratic National Committee then brought this appeal under 28 U. S. C. § 1257 (2).
Wisconsin held its primary on April 1, 1980, in accord with its election laws. Subsequently, the State Party chose delegates to the 1980 Democratic National Convention, in compliance with the order of the Wisconsin Supreme Court and Wis. Stat. §§ 8.12 (3)(b), (3)(c) 5 (1977). This Court noted probable jurisdiction of the appeal on July 2, 1980. 448 U. S. 909. On the same day, the Court stayed the judgment of [115]*115the Wisconsin Supreme Court. On July 20, 1980, the Credentials Committee of the National Convention decided to seat the delegates from Wisconsin, despite this Court’s stay,12 and despite the delegates’ selection in a manner that violated Rule 2A.13
II
Rule 2A can be traced to efforts of the National Party to study and reform its nominating procedures and internal structure after the 1968 Democratic National Convention.14 [116]*116The Convention, the Party’s highest governing authority, directed the Democratic National Committee (DNC) to establish a Commission on Party Structure and Delegate Selection (McGovern/Fraser Commission). This Commission concluded that a major problem faced by the Party was that rank-and-file Party members had been underrepresented at its Convention, and that the Party should “find methods which would guarantee every American who claims a stake in the Democratic Party the opportunity to make his judgment felt in the presidential nominating process.” Commission on Party Structure and Delegate Selection, Mandate for Reform: A Report of the Commission on Party Structure and Delegate Selection to the Democratic National Committee 8 (Apr. 1970) (emphasis added) (hereafter Mandate for Reform). The Commission stressed that Party nominating procedures should be as open and accessible as possible to all persons who wished to join the Party,15 but expressed the concern that “a full opportunity for all Democrats to participate is diluted if members of other political parties are allowed to participate [117]*117in the selection of delegates to the Democratic National Convention.” Id., at 4:7.16
The 1972 Democratic National Convention also established a Commission on Delegate Selection and Party Structure (Mikulski Commission). This Commission reiterated many of the principles announced by the McGovern/Fraser Commission, but went further to propose binding rules directing state parties to restrict participation in the delegate selection process to Democratic voters. Commission on Delegate Selection and Party Structure, Democrats All: A Report of the Commission on Delegate Selection and Party Structure 2, 15 (Dec. 6, 1973) (hereafter Democrats All). The DNC incorporated these recommendations into the Delegate Selection Rules for the 1976 Convention. In 1974, the National Party adopted its charter and by-laws. The charter set the following qualifications for delegates to the Party’s national conventions:
“The National Convention shall be composed of delegates who are chosen through processes which (i) assure all Democratic voters full, timely and equal opportunity to participate and include affirmative action programs toward that end, (ii) assure that delegations fairly reflect the division of preferences expressed by those who participate in the presidential nominating process,. . . [and] (v) restrict participation to Democrats only . . . .” Democratic National Committee, Charter of the Democratic Party of the United States, Art. Two, § 4 (emphasis added).
[118]*118Rule 2A took its present form in 1976. Consistent with the charter, it restricted participation in the delegate selection process in primaries or caucuses to “Democratic voters only who publicly declare their party preference and have that preference publicly recorded.” But the 1976 Delegate Selection Rules allowed for an exemption from any rule, including Rule 2A, that was inconsistent with state law if the state party was unable to secure changes in the law.17
In 1975, the Party established yet another commission to review its nominating procedures, the Commission on Presidential Nomination and Party Structure (Winograd Commission). This Commission was particularly concerned with what it believed to be the dilution of the voting strength of Party members in States sponsoring open or “crossover” primaries.18 Indeed, the Commission based its concern in part on a study of voting behavior in Wisconsin’s open primary. See Adamany, Cross-Over Voting and the Democratic Party’s Reform Rules, 70 Am. Pol. Sci. Rev. 536, 538-539 (1976).
The Adamany study, assessing the Wisconsin Democratic primaries from 1964 to 1972, found that crossover voters comprised 26% to 34% of the primary voters; that the voting patterns of crossover voters differed significantly from those of participants who identified themselves as Democrats; and that crossover voters altered the composition of the delegate slate chosen from Wisconsin.19 The Winograd Commission [119]*119thus recommended that the Party strengthen its rules against crossover voting, Openness, Participation and Party Building: Reforms for a Stronger Democratic Party 68 (Feb. 17, 1978) (hereafter Openness, Participation), predicting that continued crossover voting “could result in a convention delegation which did not fairly reflect the division of preferences among Democratic identifiers in the electorate.” Ibid. And it specifically recommended that “participation in the delegate selection process in primaries or caucuses ... be restricted to Democratic voters only who publicly declare their party preference and have that preference publicly recorded.” Id., at 69. Accordingly, the text of Rule 2A was retained, but a new Rule, 2B, was added, prohibiting any exemptions from [120]*120Rule 2A. Delegate Selection Rules for the 1980 Democratic Convention, Rule 2B.20
Ill
The question in this case is not whether Wisconsin may conduct an open primary election if it chooses to do so, or whether the National Party may require Wisconsin to limit its primary election to publicly declared Democrats.21 Rather, the question is whether, once Wisconsin has opened its Democratic Presidential preference primary to voters who do not publicly declare their party affiliation, it may then bind the National Party to honor the binding primary results, even though those results were reached in a manner contrary to National Party rules.
The Wisconsin Supreme Court considered the question before it to be the constitutionality of the “open” feature of the state primary election law, as such. Concluding that the [121]*121open primary serves compelling state interests by encouraging voter participation, the court held the state open primary constitutionally valid. Upon this issue, the Wisconsin Supreme Court may well be correct. In any event, there is no need to question its conclusion here. For the rules of the National Party do not challenge the authority of a State to conduct an open primary, so long as it is not binding on the National Party Convention. The issue is whether the State may compel the National Party to seat a delegation chosen in a way that violates the rules of the Party. And this issue was resolved, we believe, in Cousins v. Wigoda, 419 U. S. 477.
In Cousins the Court reviewed the decision of an Illinois court holding that state law exclusively governed the seating of a state delegation at the 1972 Democratic National Convention, and enjoining the National Party from refusing to seat delegates selected in a manner in accord with state law although contrary to National Party rules. Certiorari was granted “to decide the important question . . . whether the [a]ppellate [c]ourt was correct in according primacy to state law over the National Political Party’s rules in the determination of the qualifications and eligibility of delegates to the Party’s National Convention.” Id., at 483. The Court reversed the state judgment, holding that “Illinois’ interest in protecting the integrity of its electoral process cannot be deemed compelling in the context of the selection of delegates to the National Party Convention.” Id., at 491. That disposition controls here.
The Cousins Court relied upon the principle that “[t]he National Democratic Party and its adherents enjoy a constitutionally protected right of political association.” Id., at 487. See also, id., at 491 (Rehnquist, J., concurring). This First Amendment freedom to gather in association for the purpose of advancing shared beliefs is protected by the Fourteenth Amendment from infringement by any State. Kusper v. Pontikes, 414 U. S. 51, 57; Williams v. Rhodes, 383 U. S. 23, 30-31. See also NAACP v. Alabama ex rel. Patterson, [122]*122357 U. S. 449, 460. And the freedom to associate for the “common advancement of political beliefs,” Kusper v. Pontikes, supra, at 56, necessarily presupposes the freedom to identify the people who constitute the association, and to limit the association to those people only.22 “Any interference with the freedom of a party is simultaneously an interference with the freedom of its adherents.” Sweezy v. New Hampshire, 354 U. S. 234, 250; see NAACP v. Button, 371 U. S. 415, 431.
Here, the members of the National Party, speaking through their rules, chose to define their associational rights by limiting those who could participate in the processes leading to the selection of delegates to their National Convention. On several occasions this Court has recognized that the inclusion of persons unaffiliated with a political party may seriously distort its collective decisions — thus impairing the party’s essential functions — and that political parties may accordingly protect themselves “from intrusion by those with adverse political principles.” Ray v. Blair, 343 U. S. 214, 221-222. In Rosario v. Rockefeller, 410 U. S. 752, for example, the Court sustained the constitutionality of a requirement — there imposed by a state statute — that a voter enroll in the party of his choice at least 30 days before the general election in order to vote in the next party primary. The purpose of that statute was “to inhibit party ‘raiding,’ whereby voters in sympathy with one party designate themselves as voters of another party so as to influence or determine the results of the other party’s primary.” Id., at 760.23 See also Kusper v. Pontikes, supra, at 59-60.
[123]*123The Wisconsin Supreme Court recognized these constitutional doctrines in stating that the National Party could exclude persons who are not Democrats from the procedures through which the Party’s national candidates are actually chosen. 93 Wis. 2d, at 499, 287 N. W. 2d, at 530. But the court distinguished Cousins on the ground that this case “does not arise 'in the context of the selection of delegations to the National Party Convention. . . .’”24 Id., at 525, 287 N. W. 2d, at 543. The court’s order, however, unequivocally obligated the National Party to accept the delegation to the National Convention chosen in accord with Wisconsin law, despite contrary National Party rules.
The State argues that its law places only a minor burden on the National Party. The National Party argues that the burden is substantial, because it prevents the Party from “screen [ing] out those whose affiliation is . . . slight, tenuous, or fleeting,” and that such screening is essential to build a more effective and responsible Party. But it is not for the courts to mediate the merits of this dispute. For even if the State were correct,25 a State, or a court, may not con[124]*124stitutionally substitute its own judgment for that of the Party. A political party’s choice among the various ways of determining the makeup of a State’s delegation to the party’s national convention is protected by the Constitution.26 And as is true of all expressions of First Amendment freedoms, the courts may not interfere on the ground that they view a particular expression as unwise or irrational.27
IV
We must consider, finally, whether the State has compelling interests that justify the imposition of its will upon the appellants. See Cousins, 419 U. S., at 489.28 “Neither the right to associate nor the right to participate in political activities is absolute.” CSC v. Letter Carriers, 413 U. S. 548, 567. The State asserts a compelling interest in preserving the overall integrity of the electoral process, providing secrecy [125]*125of the ballot, increasing voter participation in primaries, and preventing harassment of voters.29 But all those interests go to the conduct of the Presidential preference primary — not to the imposition of voting requirements upon those who, in a separate process, are eventually selected as delegates.30 Therefore, the interests advanced by the State31 do not justify [126]*126its substantial32 intrusion into the associational freedom of members of the National Party.
V
The State has a substantial interest in the manner in which its elections are conducted, and the National Party has a substantial interest in the manner in which the delegates to its National Convention are selected. But these interests are not incompatible, and to the limited extent they clash in this case, both interests can be preserved. The National Party rules do not forbid Wisconsin to conduct an open primary. But if Wisconsin does open its primary, it cannot require that Wisconsin delegates to the National Party Convention vote there in accordance with the primary results, if to do so would violate Party rules. Since the Wisconsin Supreme Court has declared that the National Party cannot disqualify delegates who are bound to vote in accordance with the results of the Wisconsin open primary, its judgment is reversed.
It is so ordered.