ON RELATOR’S PETITION FOR WRIT OF MANDAMUS
REEVES, Chief Justice.
Relator Jeff Wentworth seeks a writ of mandamus directing respondent Fred Meyer, Chairman of the State Republican Executive Committee, to place Wentworth’s name on the November, 1992 general election ballot as Republican Party nominee for state senate, district 26. Meyer determined that Wentworth is ineligible to be a candidate for that office according to the provisions of Tex.Const. art. Ill, § 19, because the board of regents term to which Wentworth had been appointed will not have expired by the time he would take office as senator. We deny the petition for writ of mandamus.
[151]*151A “court of appeals may issue a writ of mandamus to compel the performance of any duty imposed by law in connection with the holding of an election .. regardless of whether the person responsible for performing the duty is a public officer.” Tex.Elec.Code Ann. § 273.061 (Vernon 1986). The writ will issue to enforce a duty placed by the election code on an officer of a political party. Tex.Elec. Code Ann. § 161.009 (Vernon 1986). See also Oney v. Ammerman, 458 S.W.2d 54, 54 (Tex.1970) (writ will issue only upon a showing that an election officer has failed to perform a duty “clearly fixed and required by the law.”). This standard is in line with the traditional use of the writ to compel the performance of a ministerial act or duty. See Walker v. Packer, 827 S.W.2d 833, 838-39 (Tex.1992).
Mandamus will also issue to correct a “clear abuse of discretion.” Id. at 839. A clear abuse of discretion occurs whenever the trial court reaches a decision that is “so arbitrary and unreasonable as to amount to a clear and prejudicial error of law.” Johnson v. Fourth Court of Appeals, 700 S.W.2d 916, 917 (Tex.1985). A relator who attacks the ruling as an abuse of discretion has the heavy burden to establish, under the circumstances of the case, that the facts and law permit the trial court to make but one decision. Id. Even if the reviewing court would have decided the issue differently, it cannot disturb the trial court’s decision unless it is shown to be arbitrary and unreasonable. Walker, at 839; Johnson 700 S.W.2d at 918. We see no reason to review the actions of an election officer by a different standard than those of a trial judge.
Wentworth raises three arguments: he is not constitutionally ineligible to stand as a candidate for state senator, his eligibility for office has been established by the doctrines of res judicata and law of the case, and Meyer abused his discretion in declaring him ineligible because the public record does not conclusively establish his ineligibility.
I.
On April 24, 1992, following a runoff election in which Wentworth was selected by the Republican voters of his district as nominee for state senator, Meyer certified to the Secretary of State that Wentworth was the Republican Party’s nominee for that office. Wentworth received from Meyer a certificate of nomination. Three weeks later, however, Meyer sent notification to Wentworth and to the Secretary of State that Wentworth is ineligible to hold that office. See Tex.Elec.Code Ann. § 145.003 (Vernon 1986).
In his letter to Wentworth, Meyer cited article III, section 19 as authority for his decision. That section provides:
No judge of any court, Secretary of State, Attorney General, clerk of any court of record, or any person holding a lucrative office under the United States, or this State, or any foreign government shall during the term for which he is elected or appointed, be eligible to the Legislature.
(emphasis added). One ineligible to hold an office cannot be a candidate for that office. Tex.Elec.Code Ann. § 141.001(a) (Vernon 1986). On March 24,1987, Wentworth was appointed by the Governor and confirmed by the senate to be a member of the Board of Regents of the Texas State University System for a six-year term expiring February 1, 1993.1 He was confirmed by the senate on April 9, 1987. The term of the legislative office Wentworth seeks will commence on January 12, 1993, and overlaps by 19 days the term of office as regent.
Wentworth resigned his position as regent on May 10, 1988, over four years ago, to take office as a state representative. Wentworth was elected to the house of representatives in a special election held in May 1988. He was sworn in the day after he resigned his position as regent. He was [152]*152re-elected to the house in November 1988 and November 1990. He is presently a member of that body, and his current term does not expire until the 73rd Legislature convenes on January 12, 1993.
Any constitutional or statutory provision that restricts the right to hold public office is to be strictly construed in favor of eligibility. Dawkins v. Meyer, 825 S.W.2d 444, 448 (Tex.1992); Willis v. Potts, 377 S.W.2d 622, 623 (Tex.1964). On the other hand, we are not free to question the wisdom of the constitution, but we must give full effect to its plain language. Dawkins, 825 S.W.2d at 448. In construing the language of the constitution, we consider the intent of the people who adopted it. Edgewood Indep. Sch. Dist. v. Kirby, 777 S.W.2d 391, 394 (Tex.1989). Because of the inherent difficulty in determining the intent of voters over a century ago, we must rely heavily on the constitution’s literal text. Id. Further, we are duty-bound to follow the decisions and authoritative expressions of the supreme court. Lofton v. Texas Brine Corp., 777 S.W.2d 384, 386 (Tex.1989); Lumpkin v. H & C Communications, Inc., 755 S.W.2d 538, 540 (Tex. App. — Houston [1st Dist.] 1988, writ denied).2
The “during the term” phrase of section 19 has always been literally construed. In Lee v. Daniels, 377 S.W.2d 618 (Tex.1964), Sam Jorrie, a Bexar County Commissioner, resigned his office effective February 1, 1964, so he could enter the primary in May of that year to run for the house of representatives. A party official was manda-mused to remove his name from the ballot because his commissioners’ court term would overlap the house term he sought by nearly two months. The supreme court held that Jorrie was ineligible. The court held that under section 19 it is the term that controls; Jorrie was ineligible to hold legislative office during the term of office of county commissioner to which he had been elected. Id. at 619-20. Nothing Jor-rie did after he qualified for and began holding his office as commissioner, including his resignation, could affect his eligibility. Id. at 620. “We construe the constitutional provision as allowing no exceptions as to ineligibility once it has been established.” Id. (emphasis added).
A similar result was reached in Kirk v. Gordon, 376 S.W.2d 560 (Tex.1964). In Kirk, the supreme court held that district attorney Tom Todd was ineligible to be a candidate for state representative. The court relied on section 19 and on Tex.Const. art. Ill, § 4, which provides that representatives’ terms “shall be two years from the day of their election.” Because Todd, if elected, would commence his house term in November, that term would overlap his term as district attorney, which would not expire until the end of that year. Kirk, 376 S.W.2d at 561.
When Wentworth took office as regent, he became ineligible for a legislative office that would commence prior to the expiration of his term as regent. Once this ineligibility is established, section 19 provides no exceptions that would allow Went-worth to hold such office. Lee, 377 S.W.2d at 620.
Since it is the term which controls, it makes no material difference whether the holder of the office resigns the day after he actually begins holding that office, the day of filing for the office of legislator, or the day before the election at which time the term of office of members of the Legislature begins.
Id. at 619. We are bound by the interpretation of section 19 as enunciated by the supreme court in Lee and Kirk. We thus have no choice but to apply that interpreta[153]*153tion in this case and to hold that Went-worth is ineligible for the office he seeks.3
Wentworth relies largely on Spears v. Davis, 398 S.W.2d 921 (Tex.1966). In that case relators Franklin Spears and Galloway Calhoun, Jr., who were then state senators, sought writs of mandamus ordering Will D. Davis, the chairman of the State Democratic Executive Committee, to place their names on the primary ballot as candidates for nomination for the office of attorney general for a two-year term commencing on January 1,1967. Spears had been elected to a four-year senate term in November of 1962, and Calhoun was elected in November, 1964. At issue was their eligibility to serve as attorney general under Tex. Const, art. Ill, § 18 which provided in part:
No Senator or Representative shall, during the term for which he may be elected, be eligible to any civil office of profit under this State, which shall have been created, or the emoluments of which may have been increased during such term....
Both relators were members of the legislature which raised the attorney general’s salary. For this reason they were constitutionally ineligible to serve as attorney general during their legislative terms. The issue in Spears was when the relators’ four-year terms began. The constitution at that time did not fix a definite time for the commencement of senators’ terms. Davis argued that senators’ terms began with the convening of the legislature in early January. If this were true, the relators’ current senatorial terms would extend several days beyond the commencement of the attorney general’s.
To complicate matters for the relators, a 1965 amendment to the Election Code required that a canvass of the returns of a legislative election would take place on the Monday before the second Tuesday in January following the election. At the time this amendment was enacted there was ample authority that an election was not complete until the returns had been canvassed. If the relators’ terms commenced on this date, they would overlap with the term of the attorney general, and section 18 would make the relators ineligible for that office. The supreme court held that it could not have been the legislature’s intention by this amendment to extend the senators’ terms into January, and thus create an overlap and render them ineligible for the office of attorney general. Id. at 924. The court held that the amendment to the Election Code was clearly intended to operate prospectively. Id. Thus, it did not apply to the relators who were serving their senatorial terms when the amendment was enacted.
The court then addressed the relators’ primary contention and held that a senatorial term begins on the day of the general election. Id. at 927. The court based its decision on the distinction between “term of office” and “tenure in office” and the fact that the constitution fixed representatives’ terms “from the day of their election.” Tex.Const. art. Ill, § 4. The court reasoned that because the senate and the house are together styled “the legislature” by the constitution, senators’ terms should begin on the same day as representatives’ terms. Because there was thus no overlap between Spears’ senate term and that of the attorney general, the court held that Spears was eligible for the office of attorney general.4 Id. at 928.
[154]*154Although Calhoun was elected two years later than Spears, his term was subject to the apportionment clause, which effectively terminated his term on November 8, 1966. The court thus held that he too was eligible for the attorney general term commencing on January 1, 1967. Id. at 929.
Section 18 was amended subsequent to the Spears decision to add the following language:
provided, however, the fact that the term of office of Senators and Representatives does not end precisely on the last day of December but extends a few days into January of the succeeding year shall be considered as de minimus, and the ineligibility herein created shall terminate on the last day in December of the last full calendar year of the term for which he was elected.
(emphasis added). It must be concluded that this amendment was necessary because of the prospective operation of the 1965 Election Code amendment. It was necessary to add the de minimus language to section 18 to ensure that the overlaps created by the 1965 amendment did not disqualify legislators as candidates for state office.
Spears is distinguishable because it is not an overlap case. The supreme court clearly concluded that the relators’ senatorial terms ended before that of the attorney general began. Spears is cited to us, however, primarily for the principle that both the purpose of the constitutional provision and the intention of the legislature in passing any laws that might affect eligibility for office should be looked to in order to determine a candidate’s eligibility to seek and hold office. Wentworth contends that the 19-day overlap did not exist prior to 1983 when the legislature, in Senate Bill 194,5 moved the end of the terms of various appointive offices, including that of Texas State University System regent,6 from January 1 to February 1 of every odd-numbered year. Wentworth argues that the legislature’s intent in passing Senate Bill 194 was only to prevent an outgoing governor, whose term expires in mid-January, from making a rash of “midnight” appointments prior to the incoming governor’s taking office.7 He asserts that it was not the intention of the legislature to render persons such as himself ineligible for office.8 He also urges that the 19-day overlap is inconsequential and de minimis.
We cannot agree that the overlap created by Senate Bill 194 is de minimus and does not affect eligibility to seek and hold legislative office merely because the legislature may not have intended to deny this eligibility to appointive officeholders such as Wentworth. The legislature’s intention in its enactment of Senate Bill 194 is irrelevant to this proceeding. We must concern ourselves with the actual effect of the enactment, not with what the legislature may or may not have intended it to do. The legislature cannot by statutory enactment authorize what the constitution prohibits. Maher v. Lasater, 163 Tex. 356, 354 S.W.2d 923, 925 (1962). It is presumed that the legislature is familiar with the state constitution, Spence v. Fenchler, 107 Tex. 443, 180 S.W. 597, 605 (1915), and intended compliance with it, Tex.Gov’t Code Ann. § 311.021(1) (Vernon 1988). “A [155]*155statute is presumed to have been enacted by the legislature with complete knowledge of the existing law and with reference to it.” Acker v. Texas Water Comm’n, 790 S.W.2d 299, 301 (Tex.1990). We must presume that the legislature was well aware of section 19’s application to legislative office seekers.9
Senate Bill 194 took effect June 19,1983. Wentworth took office as regent in March, 1987. If we were to follow the reasoning in Spears in an attempt to hold that Senate Bill 194 has no application to Wentworth, we would be holding that it has no prospective application at all.10 We would also be ignoring its express language, its plain effect (the creation of an overlap), and the express language of section 19 as interpreted by the supreme court.
The people of Texas have not passed an amendment to section 19 similar to the de minimus amendment to section 18. We cannot do it for them by holding that the overlap in this case is de minimus. See Dawkins, 825 S.W.2d at 450 (“the power to change such a [harsh] result by amending our constitution lies not in our hands, but in the hands of the sovereign people of the State of Texas.”).
II.
Wentworth next maintains that his eligibility for the office of senator has been established by the doctrines of res judicata and the law of the case. The legislature’s authority under article III, section 8 is judicial in nature. See Tex.Const. art. Ill, § 8, interpretative commentary. From this Wentworth argues that the legislature, having already seated him three times under the same facts that exist in this case, has established the law of the case and that his eligibility to hold office as a senator is established by res judicata. He argues that the legislature’s decision to seat him is “unassailable, is not subject to collateral attack, nor subject to judicial review.”
Each house of the legislature is the sole judge of the qualifications and election of its own members. Tex.Const. art. Ill, § 8. See also Kirk, 376 S.W.2d at 562; Burroughs v. Lyles, 142 Tex. 704, 181 S.W.2d 570, 575 (1944). This court does not question the legislature’s power in that regard, however, the legislature has devised procedures for keeping ineligible candidates off the ballot in the first place. See, e.g., Tex.Elec.Code Ann. §§ 141.032, 145.-003 (Vernon 1986). Article III, section 8 does not prohibit the legislature from doing so. Burroughs, 181 S.W.2d at 575. The legislature may adopt all regulations reasonably necessary to avoid the futility of electing one who is not eligible to hold the office. Id. Further, the courts may review by mandamus the actions of persons upon whom duties are imposed by law in connection with the holding of an election or a party convention. See, e.g., Sears v. Bayoud, 786 S.W.2d 248, 249 (Tex.1990); Kirk, 376 S.W.2d at 562; Burroughs, 181 S.W.2d at 572. The legislature has specifically provided us with this authority. Tex. Elec.Code Ann. §§ 161.009 and 273.061 (Vernon 1986).11
The doctrine of res judicata encompasses the separate judicial doctrines of merger, bar, and collateral estoppel. Puga v. Donna Fruit Co., 634 S.W.2d 677, 679 (Tex.1982). Res judicata bars retrial of claims that have been actually litigated and finally adjudicated in the original suit. See Coalition of Cities for Affordable Util. Rates v. Public Util. Comm’n, 798 S.W.2d 560, 562-63 (Tex.1990), cert. denied sub nom., Gulf States Utils. Co. v. Coalition of Cities for Affordable Util. Rates, — [156]*156U.S.-, 111 S.Ct. 1641, 113 L.Ed.2d 736 (1991) (finally adjudicated); Jeanes v. Henderson, 688 S.W.2d 100, 103 (Tex.1985) (actually litigated). It also bars litigation of all issues connected with a cause of action or defense which, with the use of diligence, might have been litigated in the prior suit. Bonniwell v. Beech Aircraft Corp., 663 S.W.2d 816, 818 (Tex.1984). “When a prior judgment is offered in a subsequent suit in which there is identity of parties, issues and subject matter, such judgment is treated as an absolute bar to retrial of claims pertaining to the same cause of action on the theory that they have merged into the judgment.” Id.
Wentworth has shown us nothing to indicate that the house actually considered (“adjudicated”) his eligibility to sit as a representative. We cannot presume from the state of the record that Went-worth’s qualifications to hold office were ever reviewed by the house. The mere fact that Wentworth was allowed to take his seat does not raise the presumption that that matter was “actually litigated” in the house.12 Res judicata’s requirement of a final judgment presupposes that a trial has taken place. See Coalition of Cities, 798 S.W.2d at 563 (“All of the same parties participated vigorously in the initial contest with each presenting its own evidence and cross-examining its opponent’s witnesses. Were this not true, imposition of res judi-cata principles would be inappropriate.”).
Furthermore, there is no indication that Meyer has previously challenged Wentworth’s eligibility before the house or before any other forum. Thus, the requirement of identity of parties is not met. The doctrine of res judicata does not apply.13
The doctrine of the law of the case is likewise inapplicable. The law of the case is established when a question of law is determined on appeal by a court of last resort. Hudson v. Wakefield, 711 S.W.2d 628, 630 (Tex.1986). The determination will govern a case in all subsequent stages, including retrial and subsequent appeal. Id.; Dessommes v. Dessommes, 543 S.W.2d 165, 169 (Tex.Civ.App. — Texarkana 1976, writ ref’d n.r.e.). As with res judica-ta, the doctrine of the law of the case presupposes that the question of law has been fully and fairly litigated in a prior trial. There is no indication in the record that the issue of Wentworth’s qualifications to sit as a legislator has been previously contested.
Wentworth argues that the facts establishing the overlapping terms were matters of public record which the house was presumed to know. He argues that with “full knowledge” of Meyer’s position regarding his ineligibility, “the Legislature decided against the position espoused by the Respondent_” There is no indication, however, that Meyer has ever before challenged Wentworth’s eligibility. Further, facts may exist establishing a cause of action in one’s favor, but unless the matter is litigated, a final judgment that is res judicata can never be obtained.
Section 8 provides that each house is the judge of the qualifications of its members. Even if it can be said that the house has made a judicial determination that Went-worth is qualified to hold his seat as representative, the senate has not “adjudicated” Wentworth’s eligibility to sit in that cham[157]*157ber, and the house’s determination will not bind the senate.
III.
Finally, Wentworth contends that Meyer has abused his discretion because Wentworth’s ineligibility is not conclusively established in the public record. Meyer, as Republican Party Chairman, may declare a candidate ineligible before the 30th day preceding the general election if “facts indicating that the candidate is ineligible are conclusively established by another public record.” Tex.Elec.Code Ann. §§ 145.003(b) and 145.003(f)(2) (Vernon 1986). See also Sears, 786 S.W.2d at 253-54.
Wentworth has submitted several exhibits chronicling his appointment and confirmation as regent, his resignation, the nomination of George William Worth as his successor, the senate’s rejection of Worth’s nomination a year later, and the nomination and confirmation of Clyde Waddell, Jr. to the board of regents.
Wentworth places particular emphasis on the report of the senate committee on nominations confirming Waddell as “filling [the] unexpired term of Mr. George Worth.” From this he argues that because the senate record shows that it was Worth’s rather than Wentworth’s unexpired term that was being filled, Wentworth’s ineligibility was not “conclusively established” by the public record.
On the contrary, the public record of Wentworth’s nomination is a letter by then-governor William P. Clements to the senate nominating him “TO BE A MEMBER OF THE TEXAS STATE UNIVERSITY SYSTEM BOARD OF REGENTS FOR A TERM TO EXPIRE 2-1-93.” The public record establishes that the senate confirmed his nomination. It is public record that the next senate will convene in regular session on January 12, 1993, the second Tuesday in January. The constitution provides that senators take office on the convening of the regular session of the legislature following their election. Tex.Const. art. Ill, § 3. The public record thus conclusively establishes that the regent’s term to which Wentworth was appointed overlaps by 19 days the senate term he seeks, Wentworth does not contest these facts.
It makes no difference whether Went-worth has had one, two, or several successors in office. The issue is not who or how many succeed him, but whether the public record conclusively establishes that his board of regents term will overlap the legislative term sought. Under section 19, as interpreted by the supreme court, nothing Wentworth has done or can do, including his resignation four years earlier, will avoid section 19’s prohibition against overlapping terms. Lee, 377 S.W.2d at 620. Because the public record conclusively establishes Wentworth’s ineligibility, Meyer did not abuse his discretion in removing his name from the general election ballot. Meyer may not ignore facts establishing the ineligibility of a candidate; he properly declared Wentworth ineligible. See Sears, 786 S.W.2d at 254.
The result in this case is harsh and unfair to Wentworth and to those appointive officeholders similarly situated. We are loath to hold that a candidate chosen by the voters of his party is ineligible to seek and hold political office. But unless section 19 is amended, or until the supreme court alters its interpretation of that provision, we are bound by the unequivocal holding of Lee that the constitution bars officeholders from seeking election to the legislature until the expiration of their term of office, even if they have resigned. It is unfortunate that the Republican voters of district 26, without their knowledge and through no fault of their own, chose an ineligible candidate. But the issue in this case is not whether they can select the candidate of their choice. Clearly they have that power. Rather, the issue is whether Wentworth is eligible to be that candidate. Clearly, under binding precedent, he is not.
The petition for writ of mandamus is denied.