Republican presidential candidate former President Donald Trump speaks at a campaign rally Monday Oct. 23, 2023, in Derry, N.H. (AP Photo/Charles Krupa)

A trial to determine whether the 14th Amendment’s “insurrectionist ban” applies to former President Donald Trump is set to begin Monday in Denver, a historic but likely long-shot case that could block him from Colorado’s presidential ballot in 2024.

Six Republican and unaffiliated Colorado voters filed the lawsuit in early September with the backing of a liberal watchdog group called Citizens for Responsibility and Ethics in Washington, or CREW. They’re arguing that Trump is disqualified from serving as president again because of his role in the January 6, 2021, insurrection.

The challengers have scored a series of pretrial victories, defying expectations by defeating several motions by Trump and the Colorado GOP to throw out the case.

The bench trial in Colorado District Court is scheduled to last at least one week. Trump is not expected to attend. He denies wrongdoing regarding January 6, and his campaign said the challengers are “stretching the law beyond recognition.”

“It’s the first domino to fall. We’ve never seen a challenge like this to a presidential candidate, hearings that go for days to evaluate their eligibility,” said Derek Muller, an election law expert at Notre Dame Law School who filed a brief in a similar case that was neutral on disqualifying Trump but gave analysis for key legal questions.

“It’s not a frivolous lawsuit, but it’s not a slam dunk,” Muller added.

What does the 14th Amendment say?

The 14th Amendment, which was ratified after the Civil War, says US officials who take an oath to uphold the Constitution are disqualified from holding future office if they “engaged in insurrection” or have “given aid or comfort” to insurrectionists.

However, the Constitution does not spell out how to enforce the ban, and it has been applied only twice since the 1800s, when it was used against former Confederates.

The amendment’s key provision, Section 3, says in part: “No person shall … hold any office … under the United States … who, having previously taken an oath … to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof.”

What is the trial about?

The challengers sued Colorado Secretary of State Jena Griswold. They want a court order blocking Griswold from putting Trump’s name on Colorado’s GOP primary ballot and the general election ballot. Griswold, a Democrat, hasn’t taken a position on whether Trump is disqualified and said she’ll do what the judge orders her to do.

Colorado Judge Sarah Wallace had spelled out some of the key questions for trial.

• What is the definition of “engaged” and “insurrection”?
• Did Trump engage in an insurrection?
• Is the so-called insurrectionist ban self-executing, or does Congress need to take action before a candidate is disqualified?
• Does Griswold have the power under Colorado law to exclude a candidate from the ballot based on federal constitutional considerations?
• Does the ban apply to US presidents, or only to other officials?

How is Trump fighting back?

Trump has ridiculed the lawsuit at his campaign rallies. His lawyers and advisers have argued that it would be “un-American” to deprive voters the opportunity to decide whether the former president should return to the White House by removing him from the ballot.

In his attempts to throw out the lawsuit, Trump unsuccessfully argued that the case misinterpreted Colorado’s ballot access laws, that the lawsuit raised a “political question” that only Congress could decide and that it violated his free-speech rights.

“This is a political lawsuit meant to prevent President Trump from standing for election and to block Colorado voters from having the opportunity to vote for him,” Trump’s lawyers wrote in a court filing last week.

They added, “Colorado statute provides no basis for barring a presidential candidate under the Fourteenth Amendment. And President Trump never advocated for or incited violence on January 6, 2021.”

Why is this happening now?

CREW filed the lawsuit in September, asking for an expedited process to resolve the dispute before Colorado’s GOP primary on March 5, which is Super Tuesday.

Wallace has said she hopes to issue a ruling by Thanksgiving, so appeals courts in Colorado have enough time to review the matter and hand down their own decision.

Griswold has said there is a “hard deadline” of January 5 for a resolution in the case. Her office is required by that date to certify the names of all candidates that will be printed on the March 5 primary ballot.

What’s the big picture?

This is one of several lawsuits in battleground states to remove Trump from the ballot. Other advocacy groups have filed challenges in Minnesota and Michigan.

While the groups behind the lawsuits are liberal-leaning, many of the plaintiffs are Republicans. The lead plaintiff in Colorado is Norma Anderson, a Republican former state legislator who served as majority leader in the both the Colorado House and Senate.

A growing number of constitutional scholars have endorsed the challengers’ theory against Trump, including some notable conservative jurists and legal experts.

But serious divides remain how the 14th Amendment could be applied to Trump and how the ban would even be implemented, whether by election officials, Congress or a court, given the constitutional ambiguities. Many expect the Supreme Court – with its conservative supermajority – will ultimately weigh in on the matter.

Has this happened before?

There hasn’t been a case like this in history, though no US president has ever tried to overturn an election, like Trump did. It would be unprecedented to apply the 14th Amendment “insurrectionist ban” to any presidential candidate, let alone the clear front-runner for a major party nomination, as Trump is leading in the GOP polls.

The ban has been applied only once in the modern era – and CREW was behind that successful effort.

A convicted January 6 rioter who was also a New Mexico county commissioner was removed from office last year on 14th Amendment grounds through a different but related legal mechanism, after CREW filed a lawsuit.

In that case, the official had already been convicted of a January 6-related offense. Trump is facing state and federal charges related to the Capitol riot and his attempts to overturn the 2020 election – but he pleaded not guilty and hasn’t gone to trial yet.

Who is the Colorado judge?

Wallace was appointed to the bench last year by Colorado Gov. Jared Polis, a Democrat. He said Wallace would fill a vacancy opening in January of this year.

Previously, she was a partner at the large law firm Ballard Spahr, where she specialized in commercial litigation, breach-of-contract matters and employment law.

She graduated from the University of Colorado Law School in 1999.