Texas Supreme Court Chief Justice Nathan Hecht is running for his last term on the high court.

But if elected, he could only serve four of the six-year term, which runs 2021 to 2027.

The reason: The Texas Constitution sets an age limit of 75 years to serve as a judge or justice of an appellate or district court in the Lone Star State.

Hecht, who's running unopposed in the Republican Primary in March, will reach the 75-year milestone Aug. 15, 2024. The date would fall within the first four years of his term, and in that situation, Texas Constitution Article 5, Sec. 1-a, requires his seat to become vacant at the end of the fourth year of his term.

It would mean Dec. 31, 2024, would be his last day on the court, where he's served since 1988.

"I still have a lot to do, and I want to pursue it to the end," Hecht said. "We're still trying to improve technology in the judiciary. We're working on reforms in collections of fines and fees, in how bail is set, just a number of things that have to do with the administration of the judiciary that I've done a lot of work on, and I want to continue to work on. Certainly, access to justice."

The Texas Legislature in 2007 passed—and voters later approved—a constitutional amendment to set an age limit of 75 for judges and justices in Texas.

After Hecht's retirement in 2024, the Texas governor at that time would get to appoint a chief justice to serve from Jan. 1, 2025 to Dec. 31, 2027.

If Texas Gov. Greg Abbott is still governor then, and did get to appoint a replacement for Hecht in 2025, that appointee would be the fourth justice that the governor has appointed to the high court. Abbott has also appointed Jimmy Blacklock, Brett Busby and Jane Bland.

The last time the chief justice seat was vacant was in 2013, when then-Chief Justice Wallace Jefferson retired from the high court and returned to private practice. Then-Gov. Rick Perry chose Hecht, an associate justice at the time, to ascend to the chief position. Voters then elected Hecht as chief justice in 2014.

If history repeats itself, it's likely that Hecht would win another term. Texas voters have not elected a Democrat to statewide office since 1990, although political pundits lately have voiced opinions that the state might finally be "turning blue" in 2020.

The Democratic candidates running for chief justice in March are 201st District Judge Amy Clark Meachum of Austin and 14th Court of Appeals Justice Jerry Zimmerer of Houston. The winner of their race will oppose Hecht in November.

Related: 206 Texas Democrats Are Vying for Judgeships in the March Election

Meachum wrote in an email that the race is historic in two ways.

"Texans have the opportunity to elect the first woman ever to serve as chief justice of the Supreme Court of Texas, or Texans can elect the first chief justice ever constitutionally prohibited from serving a full term," she said. "It's time for the next generation of judicial leaders to provide some much needed balance on the all-Republican Supreme Court."

Zimmerer said he doesn't question Hecht's intention to serve four more years, and doesn't hold any ill will toward him for desiring to do so.

"I think it would be almost inappropriate for me, as a Democrat, to challenge him simply on the basis of age. It's not why I'm running for the position. I'm running because I believe I'm the best candidate for the job," Zimmerer said. "I believe that Texans deserve more."