The supreme court found that an excessive, unexplained delay in filing a mandamus petition barred relief in In re Self, observing:
Relators filed this mandamus petition on August 8, 2022. The petition seeks relief within eighteen days, by August 26, which relators contend is the deadline established by the Election Code for the relief they seek. The Libertarian Party nominated the disputed candidates, who had not paid the filing fee, in April 2022. Under relators’ view of the law, those candidates’ ineligibility attached in April 2022, when they were nominated despite not paying the fee. Nearly four months passed between the facts giving rise to the relators’ claims and the filing of this mandamus action. Relators do not provide any explanation for why these claims could not have been investigated and brought to the courts with the “unusual dispatch” our precedent requires of those who seek to use the court system to alter the conduct of elections.
(footnote omitted, emphasis added). While the “unusual dispatch” concept is unique to election-law cases, Self nevertheless provides a good general reference point for when laches will bar mandamus relief in civil cases more generally. No. 22-0658 (Tex. Aug. 26, 2022).