Denver, Colorado - A Colorado court began hearing a lawsuit on Monday that seeks to bar Donald Trump from the 2024 presidential ballot on the grounds he violated his oath of office by engaging in an insurrection.

The lawsuit filed by Citizens for Responsibility and Ethics (CREW), a Washington-based watchdog group, claims Trump is ineligible to run for the White House again because of the January 6, 2021 attack on the Capitol by his supporters.

The argument, which has legal scholars sharply divided, rests on an amendment to the Constitution ratified after the 1861-65 Civil War.

Section 3 of the 14th Amendment bars anyone from holding public office if they engaged in "insurrection or rebellion" after once pledging to support and defend the Constitution. The amendment, ratified in 1868, was aimed at preventing supporters of the slave-holding Confederacy from being elected to Congress or from holding federal positions.

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The case, one of several similar legal efforts to keep the former president out of the running, is likely to end up before the Supreme Court, where conservatives hold a 6-3 majority.

Acting on behalf of six Colorado voters, CREW petitioned the Colorado Secretary of State, the top election official in the state, to keep Trump off the ballot in next year's presidential election.

"Trump incited a violent mob to attack our Capitol to stop the peaceful transfer of power under our Constitution," Eric Olson, an attorney for CREW, said in his opening argument at the live-streamed hearing being held in Denver before Judge Sarah Wallace. "January 6 was an insurrection against the Constitution. Trump engaged in that insurrection."

"We are here because Trump claims that after all that, he has the right to be president again," Olson added. "But our Constitution, our shared charter of our nation, says he cannot do so."

Scott Gessler, a former Colorado Secretary of State representing Trump, countered that the suit was "anti-democratic" and urged the judge to throw it out.

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"When it comes to deciding who should lead our nation, it's the people of the United States of America that gets to make those decisions," Gessler said. "We have elections... This is a case of lawfare that seeks to interfere with the presidential election."

The Minnesota Supreme Court is to hear a similar case on Thursday in which several voters are seeking to bar Trump from the ballot in the northern state.