The Colorado Supreme Court, in a 4-3 decision, has declared former President Donald Trump ineligible for the White House under the 14th Amendment's insurrection clause, marking the first time Section 3 of the amendment has been used to disqualify a presidential candidate.

The court overturned a district judge's ruling that Trump could not be barred from the state's presidential primary ballot.

The decision, which must be settled by January 5, sets the stage for a likely showdown in the U.S. Supreme Court.

Trump's attorneys plan to appeal, calling the ruling an attack on democracy. The Republican National Committee denounces it as election interference, fearing other states may follow suit, posing a significant threat to Trump's candidacy.

The Colorado case is the first successful use of Section 3, designed to prevent former Confederates from holding office after the Civil War.