A divided Colorado Supreme Court on Tuesday declared former President Donald Trump ineligible for the White House under the U.S. Constitution’s insurrection clause and removed him from the state’s presidential primary ballot, setting up a likely showdown in the nation’s highest court to decide whether the front-runner for the GOP nomination can remain in the race.

The decision from a court whose justices were all appointed by Democratic governors marks the first time in history that Section 3 of the 14th Amendment has been used to disqualify a presidential candidate.

“A majority of the court holds that Trump is disqualified from holding the office of president under Section 3 of the 14th Amendment,” the court wrote in its 4-3 decision.

Colorado’s highest court overturned a ruling from a district court judge who found that Trump incited an insurrection for his role in the Jan. 6, 2021, attack on the Capitol, but said he could not be barred from the ballot because it was unclear that the provision was intended to cover the presidency.

The court stayed its decision until Jan. 4, or until the U.S. Supreme Court rules on the case. Colorado officials say the issue must be settled by Jan. 5, the deadline for the state to print its presidential primary ballots.

“We do not reach these conclusions lightly,” wrote the court’s majority. “We are mindful of the magnitude and weight of the questions now before us. We are likewise mindful of our solemn duty to apply the law, without fear or favor, and without being swayed by public reaction to the decisions that the law mandates we reach.”

Trump’s attorneys had promised to appeal any disqualification immediately to the nation’s highest court, which has the final say about constitutional matters.

Trump’s legal spokeswoman Alina Habba said in a statement Tuesday night: “This ruling, issued by the Colorado Supreme Court, attacks the very heart of this nation’s democracy. It will not stand, and we trust that the Supreme Court will reverse this unconstitutional order.”

Trump didn’t mention the decision during a rally Tuesday evening in Waterloo, Iowa, but his campaign sent out a fundraising email citing what it called a “tyrannical ruling.”

Republican National Committee chairwoman Ronna McDaniel labeled the decision “Election interference” and said the RNC’s legal team intends to help Trump fight the ruling.

Trump lost Colorado by 13 percentage points in 2020 and doesn’t need the state to win next year’s presidential election. But the danger for the former president is that more courts and election officials will follow Colorado’s lead and exclude Trump from must-win states.