In the past four years, President Joe Biden has made seven appointments to the federal trial and appeals courts headquartered in Colorado, with his appointees now constituting a majority of active judges on the state’s U.S. District Court.

The next president will similarly have a chance to make his or her mark on the district court and the U.S. Court of Appeals for the 10th Circuit.

But the landscape will likely look different.

The main driver of judicial vacancies is a concept known as “senior status.” Federal judges receive lifetime appointments, but after they turn 65, have served for 10 years and the combination of their age and years of service totals 80, they may elect to become a senior judge operating with a reduced caseload.

Taking senior status also opens the seat for the president to appoint a full-time, active judge.

Since 2021, Biden appointed two 10th Circuit judges to succeed Bill Clinton appointees who went senior. He also installed five district judges to succeed a mixture of George W. Bush and Barack Obama appointees.

Recent scholarship suggests judges tend to retire under presidents who can appoint an ideologically similar successor, but the process is not wholly partisan.

For example, Judge Richard E.N. Federico, appointed to the 10th Circuit from Kansas in December, received the support of his home state Republican senators. And U.S. District Court Judge Regina M. Rodriguez, appointed in 2021, was backed by Colorado’s then-U.S. Sen. Cory Gardner, a Republican, during her original unsuccessful nomination in 2016.

With the possibility that the next president will be of a different party than the U.S. Senate’s majority, it is unclear whether judges who are eligible to go senior will choose to, or whether their successors will win confirmation. Based on the composition of the courts, here is a list of potential vacancies for the new administration.

U.S. District Court

Due to the newness of Biden’s appointees, the seven-member trial court has only one person who could take senior status: Chief Judge Philip A. Brimmer, a 2008 Bush appointee. Although Brimmer is currently eligible to go senior, he may choose to wait until his seven-year term as chief expires in 2026.

Brimmer, a former state and federal prosecutor, has handled numerous cases of political significance in recent years, including temporarily blocking lawmakers’ increase to the firearms purchasing age, rejecting the Republican Party’s request to exclude unaffiliated voters from their primaries and upholding the Biden administration’s minimum wage rule for seasonal guides. The latter case is currently on appeal to the U.S. Supreme Court.

The remaining member of the district court, Donald Trump appointee Daniel D. Domenico, will not be able to take senior status until 2037 — later than some of Biden’s appointees, even.

10th Circuit

The clear opportunity for turnover lies in the Denver-based 10th Circuit, which hears appeals from Colorado and five neighboring states. By the end of the next president’s term, eight of the 12 active judges could potentially take senior status. However, that number consists of three Republican and five Democratic appointees, making it unlikely that all eight will choose to step down.

Currently, the two longest-serving judges are eligible for senior status: Harris L Hartz, 77, of New Mexico and Timothy M. Tymkovich, 67, of Colorado. Both are Bush appointees who have been on the court for more than two decades.

Tymkovich was Colorado’s solicitor general in the 1990s, where he represented the state before the Supreme Court. He is also regularly engaged with the Federalist Society, a key organizing force for the conservative legal movement. On the 10th Circuit, Tymkovich has criticized workplace equity initiatives and authored a dissenting opinion in a free speech case that played prominently in the Supreme Court’s subsequent decision. He was also selected to serve on the nation’s wiretapping appeals court last year.

Hartz is a former state judge who recently mounted an unsuccessful campaign for Harvard’s Board of Overseers, during which he criticized liberal “groupthink” at the school. During his time on the 10th Circuit, he authored an opinion reinstating the religious freedom lawsuit of a man convicted for the World Trade Center bombing, clarified when governments can be held liable for the misconduct of their high-ranking officials and dissented from a recent decision upholding Colorado’s ban on conversion therapy for LGBTQ minors.

Chief Judge Jerome A. Holmes of Oklahoma, also a Bush appointee, will become eligible to go senior midway through the next president’s term. His seven-year term as chief runs into 2029, and Holmes may opt to remain an active judge through its entirety.

Holmes worked in private practice and the U.S. Department of Justice prior to his appointment, and one of his most well-known actions on the bench was joining a 2-1 majority to strike down a ban on same-sex marriage prior to the Supreme Court’s 2015 ruling finding such prohibitions unconstitutional. Since then, he also joined an opinion that labeled the University of Colorado’s COVID-19 vaccine mandate “hostile and discriminatory” and authored a ruling that rejected a higher hurdle for disability discrimination lawsuits.

All five Obama appointees, who joined the 10th Circuit between 2010 and 2014, will have the opportunity to go senior over the next four years. Judge Scott M. Matheson Jr. of Utah became eligible in 2022, but opted against stepping down under Biden.

Matheson was Utah’s U.S. attorney during the Clinton administration and the unsuccessful Democratic candidate for governor in 2004. As a judge, he authored an opinion recognizing the First Amendment protects the right to record police officers in public, declined to find that federal courts are prohibited entirely from hearing cannabis business disputes and found police officers could not be held liable for using a dog to attack an unarmed man.

The remaining judges who will become eligible in 2026 or 2027 are Robert E. Bacharach of Oklahoma, Gregory A. Phillips of Wyoming, Carolyn B. McHugh of Utah and Nancy L. Moritz of Kansas.

Bacharach was a federal magistrate judge before his appointment and has authored a book about legal writing. Among his appellate decisions, he wrote that Denver police officers could not be held liable for burning down a woman’s home, reinstated a conservative group’s challenge to Colorado’s ballot initiative disclosure requirements and directed immigration authorities to consider the likely persecution a transgender asylum seeker would face if deported.

Phillips was Wyoming’s attorney general when he joined the 10th Circuit. As an appellate judge, he authored decisions finding the Colorado Springs mayor could not be held liable for the cancellation of a far-right group’s conference, that a wrongly incarcerated man could not sue Denver prosecutors and law enforcement, and that El Paso County’s land-use code discriminated against some disabled persons.

McHugh was a state appellate judge prior to her appointment. As a federal judge, she wrote that Colorado Springs officers were not liable for tasing a man so much that he died, that Vail Resorts customers were not entitled to refunds for the pandemic-induced closure of ski slopes and that the government acted appropriately by approving an access road to a planned ski village in the the Rio Grande National Forest.

Moritz was a state Supreme Court justice and Court of Appeals judge before her federal appointment. Among her opinions as a circuit judge, she clarified the scope of the federal crime victim restitution law, agreed that prison employees could sue their coworkers for actually attacking them during a training exercise and that a man could not sue a police officer for confiscating his lawful hemp plants at Denver International Airport.

Of the four judges who will not reach senior status eligibility by the end of the next president’s term, two are Trump appointees and two are appointees of Biden’s.