Former President Trump is appealing landmark decisions in Colorado and Maine to remove him from the 2024 ballot due to the 14th Amendment's insurrection clause over his actions surrounding Jan. 6.

The big picture: As he appeals the Colorado case to the U.S. Supreme Court and the Maine one to a state Superior Court, two groups of voters in Illinois and Massachusetts became the latest on Thursday to file motions seeking to have him disqualified.

• At least 35 states have considered challenges to Trump's candidacy over insurrection concerns, though many of the efforts have been unsuccessful.

Context: Section 3 of the 14th Amendment states that no one should hold office in the U.S. if they "have engaged in insurrection or rebellion against the [U.S.], or given aid or comfort to the enemies thereof."

Yes, but: The provision is largely untested and the U.S. Constitution doesn't lay out how to enforce the clause to disqualify a candidate.

14th Amendment cases state of play

By the numbers: At least eight cases related to the clause have already been dismissed, including in Arizona, West Virginia, Virginia, Minnesota, Rhode Island, two in Michigan and in Florida, per legal analysis by nonprofit publication Lawfare.

• On Wednesday, Michigan's Supreme Court upheld a lower court ruling and rejected an attempt to keep Trump off the state's 2024 primary ballot.
• At least 10 cases were voluntarily withdrawn in Connecticut, Delaware, Idaho, Kansas, Utah, Oklahoma, Massachusetts, Montana and Pennsylvania.

State of play: Colorado's case is the first in which a court found that the clause applies to Trump in relation to his actions surrounding Jan. 6.

• Maine Secretary of State Shenna Bellows (D) is the first elected official to unilaterally deem Trump ineligible to run due to the 14th Amendment's insurrection clause.
• Free Speech For People is among the plaintiffs in the 14th Amendment cases, and on Thursday the nonprofit asked for a hearing with the State Board of Elections to keep Trump off the ballot.
• The advocacy group was also involved in the filing to the Massachusetts Ballot Law Commission challenging Trump's eligibility in the state.

What they're saying: Free Speech For People has argued Trump should be disqualified from office for "having engaged in insurrection and rebellion against the U.S. Constitution," beginning in late 2020 and culminating in the insurrection at the Capitol.

What he's saying: Trump, who is facing four criminal indictments, has rejected the legal theories.

• His campaign spokesperson Steven Cheung responded to the Minnesota ruling by denouncing those filing 14th Amendment lawsuits, saying "their ballot challenges should be summarily thrown out wherever they next arise."

Between the lines: Two leading conservative law professors, William Baude and Michael Paulsen, said in a September article that there are grounds for disqualifying Trump under the insurrection clause.

• "If the public record is accurate, the case is not even close," they wrote. "He is no longer eligible to the office of Presidency."
• Josh Blackman, a professor at South Texas College of Law Houston, told Stateline it would set an "extremely dangerous" precedent to let judges decide who can appear on a ballot.
• "What we're talking about here is telling people that you can't vote for the candidate of your choice," said Blackman, who co-authored a paper arguing the clause doesn't apply to Trump. "This would be the single biggest disenfranchisement in modern history."

What to watch: Many scholars believe one of the challenges will end up being determined in the U.S. Supreme Court.

Go deeper: States look to see if 14th Amendment can be used to disqualify Trump

Editor's note: This story has been updated with additional developments throughout.