The Colorado Republican Party has appealed against the state's supreme court decision to bar Donald Trump from the party's presidential primary ballot.
The appeal was lodged on Wednesday and is the potential first step to a showdown at the nation's highest court over the meaning of a 155-year-old constitutional provision banning people who "engaged in insurrection" from office.
The appeal put its ruling on pause until January 4, the day before the state's primary ballots are due at the printer, or until an appeal to the US Supreme Court is finished.
Mr Trump has said he also plans to appeal against the ruling to the nation's highest court.
The US Supreme Court has never ruled on Section 3 of the 14th Amendment, which was added after the Civil War to prevent former Confederates from returning to government.
It says that anyone who swore an oath to "support" the constitution and then "engaged in insurrection" against it cannot hold government office.
The Colorado high court ruled that does apply to Mr Trump in the wake of his role in the January 6 2021 attack on the US Capitol. It was the first time the provision was used to block a presidential contender's campaign.
"The Colorado Supreme Court has removed the leading Republican candidate from the primary and general ballots, fundamentally changing the course of American democracy," the party's lawyers wrote on Wednesday.
"Unless the Colorado Supreme Court's decision is overturned, any voter will have the power to sue to disqualify any political candidate in Colorado or any other jurisdiction that follows its lead. This will not only distort the 2024 presidential election but will also mire courts henceforth in political controversies over nebulous accusations of insurrection."
The US Supreme Court is expected to hear the case, either after the Colorado GOP's appeal or Mr Trump's.
If the former president ends up off the ballot in Colorado, it would have minimal effect on his campaign because he does not need the state, which he lost by 13 percentage points in 2020, to win the Electoral College in the presidential election. But it could open the door to courts or election officials striking him from the ballot in must-win states.
Sean Grimsley, an attorney for the plaintiffs seeking to disqualify Mr Trump in Colorado, said on a legal podcast last week that he hopes the nation's highest court hurries once it accepts the case, as he expects it will.
"We obviously are going to ask for an extremely accelerated timeline. We have a primary coming up on Super Tuesday, and we need to know the answer," he said.
More than a dozen states, including Colorado, are scheduled to hold primaries on March 5 - Super Tuesday.
No other court has sided with those who have filed dozens of lawsuits to disqualify Mr Trump under Section 3, nor has any election official been willing to remove him from the ballot unilaterally without a court order.
