Former President Donald Trump on Wednesday asked the U.S. Supreme Court to overturn a ruling barring him from the Colorado ballot, setting up a high-stakes showdown over whether a constitutional provision prohibiting those who “engaged in insurrection” will end his political career.

Trump appealed a 4-3 ruling in December by the Colorado Supreme Court that marked the first time in history that Section 3 of the 14th Amendment was used to bar a presidential contender from the ballot. The court found that Trump’s role in the Jan. 6, 2021, attack on the U.S. Capitol disqualified him under the clause.

The provision has been used so sparingly in American history that the U.S. Supreme Court has never ruled on it. Wednesday’s development came a day after Trump’s legal team filed an appeal against a ruling by Maine’s Democratic Secretary of State, Shenna Bellows, that Trump was ineligible to appear on that state’s ballot over his role in the Capitol attack. Both the Colorado Supreme Court and the Maine secretary of state’s rulings are on hold until the appeals play out.

Trump’s critics have filed dozens of lawsuits seeking to disqualify him in multiple states. He lost Colorado by 13 percentage points in 2020 and does not need to win the state to gain either the Republican presidential nomination or the presidency. But the Colorado ruling has the potential to prompt courts or secretaries of state to remove him from the ballot in other, must-win states.

None had succeeded until a slim majority of Colorado’s seven justices — all appointed by Democratic governors — ruled last month against Trump. Critics warned that it was an overreach and that the court could not simply declare that the Jan. 6 attack was an “insurrection” without a judicial process.

“The Colorado Supreme Court decision would unconstitutionally disenfranchise millions of voters in Colorado and likely be used as a template to disenfranchise tens of millions of voters nationwide,” Trump’s lawyers wrote in their appeal to the nation’s highest court, noting that Maine has already followed Colorado’s lead.