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

Jonathan Mitchell, Trump's attorney, in his opening statement, asserted that the Colorado Supreme Court decision is "wrong and should be reversed for numerous independent reasons."

Mitchell argued that Trump is not covered under Section 3 as an elected official and claiming he is not an "officer of the United States." He also said that Section 3 cannot apply to a candidate, only those who hold office.

He said that if the U.S. Supreme Court affirms the Colorado Supreme Court's decision, it would "take away votes of potentially tens of millions of Americans."

Ahead of the historic arguments, some anti-Trump demonstrators gathered outside the front of the building with banners and signs disparaging the former president.

Police also took steps to ramp up security by placing fencing around the court.

An ABC News/Ipsos poll found a majority of Americans (56%) were willing to see Trump disqualified in all or some states: 30% said the U.S. Supreme Court should bar him completely and 26% said it should let each state decide.

Thirty-nine percent said the U.S. Supreme Court should keep Trump on the ballot in all states.

Americans were split on the decisions out of Maine and Colorado to bar Trump from the ballot: 49% supported them while 46% were opposed.

There are 80 minutes total allotted for arguments but the court is expected to go over that timeframe.

A number of questions are likely to be debated: Is Trump an “officer” of the United States to whom Section 3 applies; who can enforce Section 3; and did Trump engage in an insurrection?

Trump is being represented by Jonathan Mitchell, a former clerk to Justice Antonin Scalia. The Colorado voters are being represented by Jason Murray, a former clerk to Justice Elena Kagan and Justice Neil Gorsuch.

Read more about what to expect here.