Supreme Court hears historic Trump 14th Amendment case: Key moments

The outcome could have major ramifications for the 2024 election.

The U.S. Supreme Court on Thursday heard a historic case challenging Donald Trump's ability to hold office again over his role in the Capitol attack on Jan. 6, 2021.

Trump asked the justices to overturn an unprecedented Colorado Supreme Court decision deeming him ineligible to appear on the state's GOP primary ballot because, it said, he "engaged in insurrection." Trump has long denied any wrongdoing.

The legal battle centers on a previously obscure provision of the Constitution's 14th Amendment -- Section 3 -- ratified shortly after the Civil War.

Justices skeptical of 14th Amendment case banning Trump from ballot

The nation's hight court appeared highly critical of a Colorado Supreme Court decision that would ban Trump from the state's 2024 GOP primary ballot under Section 3 of the 14th Amendment.

In more than two hours of oral arguments, each of the court's nine justices expressed skepticism that an individual state has the authority to deny a candidate for federal office from the ballot as an "insurrectionist."

While the court's ultimate decision is not always clear based on the questions raised during a hearing, it appeared likely that a majority of the court is ready to reverse the Colorado decision and put an end to efforts nationwide seeking to disqualify Trump under the rarely used, 150-year-old Constitutional provision.

Read more about takeaways from the arguments here.

-ABC News' Devin Dwyer and Isabella Murray

Trump speaks after arguments conclude

Donald Trump spoke from Mar-a-Lago in Florida moments after the arguments concluded at the U.S. Supreme Court in Washington.

The former president largely focused his criticism on President Joe Biden, but briefly addressed what transpired at the nation's high court.

"In watching the Supreme Court today, I thought it was a very beautiful process," he said. "I hope that democracy in this country will continue because right now we have a very, very tough situation with all of these radical left ideas."

Justice Alito expresses concern about states retaliating

Justice Samuel Alito, questioning the Colorado solicitor general, brought up the possibility of other states retaliating and excluding another candidate from their ballot.

Shannon Stevenson sought to downplay those concerns.

"I think we have to have faith in our system that people will follow their election processes appropriately," she said. "That they will take realistic views of what insurrection is under the 14th Amendment. Courts will review those decisions. This court may review some of them. But I don't think that this court should take those threats too seriously in its resolution of this case."

Attorney for Colorado secretary of state begins argument

Shannon Stevenson, the Colorado solicitor general, is now representing Secretary of State Jena Griswold. She is making the case that Colorado has the power, under state election code, to disqualify candidates who are ineligible to assume the office they’re seeking.

"Nothing in the Constitution strips the states of their power to direct presidential elections in this way," she said in her opening. "This case was handled capably and efficiently by the Colorado courts under a process that we've used to decide ballot changes for more than century. And as everyone agrees, the court now has the record that needs to to resolve these important issues."

Justice Jackson asks Trump lawyer what constitutes an insurrection

Justice Ketanji Brown Jackson pressed Mitchell on the Colorado Supreme Court's finding that the violent attempts by Trump supporters to halt the electoral count on Jan. 6 qualified as an "insurrection" under Section 3.

"Why would this not be an insurrection?" Jackson asked. "What's your argument that it's not?"

"For an insurrection there needs to an organized, concerted effort to overthrow the government of the United States through violence. And this riot that occurred ..." Mitchell began.

Jackson interrupted, "So, the point that a chaotic effort to overthrow the government is not an insurrection?"

"We didn't concede that it's an effort to overthrow the government either Justice Jackson, right?" Mitchell continued. "None of these criteria were met. This was a riot. It was not an insurrection. The events were shameful, violent, all those things. It was not an insurrection as that term is used in Section 3."