‘It’ll come down to just a handful of states that are going to decide the presidential election,’ the justice says.

As the U.S. Supreme Court on Thursday heard two hours of arguments in a Colorado case to remove former President Donald Trump from the ballot, Chief Justice John Roberts suggested that if he’s pulled, other states would eventually do the same to other candidates.

“It’ll come down to just a handful of states that are going to decide the presidential election,” Justice Roberts said. “That’s a pretty daunting consequence.”

Such a move, he added, would be inconsistent with the history and purpose of the Constitution’s 14th Amendment, coming about two months after Colorado’s Supreme Court ruled the former president could be barred from the state’s ballot under a provision of that amendment.

“I would expect that a goodly number of states will say: ‘Whoever the Democratic candidate is, you’re off the ballot,’” the chief justice added, speaking to Jason Murray, the lawyer representing several voters who sued to keep the former president from appearing on the Colorado ballot.

Justice Roberts asked Jonathan Mitchell, President Trump’s attorney, whether a state’s top elections official could disqualify a candidate who comes forward and says he took the oath mentioned in the provision and engaged in an insurrection.

“If the candidate is an admitted insurrectionist, Section 3 still allows the candidate to run for office and even win election to office—and then see whether Congress lifts that disability after the election,” Mr. Mitchell said.

Anti-Trump groups have sought to disqualify him in more than two dozen other states in what appears to have been a mostly unsuccessful effort over his actions after the 2020 presidential election. Days after the Colorado court ruling, Maine Secretary of State Shenna Bellows barred President Trump from its ballot, a decision on hold pending the Supreme Court’s ruling.

During the hearing, President Trump’s lawyers argued that the amendment can’t be used to keep him off the ballot for several reasons. They said that the Capitol breach during the Jan. 6 riot wasn’t an insurrection, and even if it was, President Trump did not go to the Capitol or join the rioters.

The wording of the amendment, they said, also excludes the presidency and candidates running for president. Even if they are wrong about all of that, they argue that Congress must pass legislation to reinvigorate Section 3.

The lawyers of Colorado voters who sued to remove President Trump’s name from the Colorado ballot claimed that there is ample evidence that the events of Jan. 6 constituted an insurrection and that President Trump incited it. They say it would be absurd to apply Section 3 to everything but the presidency or that the former president is somehow exempt. And the provision needs no enabling legislation, they argue.

Congress passed the 14th Amendment during the post-Civil War Reconstruction Era in a bid to clamp down on Southern states and reassert federal power.

During another portion of the hearing, Justice Roberts suggested that one of the main 14th Amendment-related arguments went against the history of the insurrection provision in the amendment.  “The whole point of the 14th Amendment was to restrict state power,” Justice Roberts said. “On the other hand, it augmented federal power.”

Justice Clarence Thomas raised a similar point during the hearing, asking Mr. Murray why there were not more examples of individual states disqualifying candidates using the 14th Amendment after the Civil War.

“There were a plethora of confederates still around, there were any number of people who would continue to either run for state offices or national offices, so it would seem—that would suggest there would at least be a few examples of national candidates being disqualified,” Justice Thomas said.

“There were certainly national candidates disqualified by Congress refusing to seat them,” Mr. Murray responded.

The Supreme Court also will hear an appeal in April from one of the more than 1,200 people charged in the Jan. 6 Capitol breach. The case could upend a charge prosecutors have brought against more than 300 people, including President Trump.

The high court last played so central a role in presidential politics in its 5–4 decision that effectively ended the disputed 2000 election in favor of George W. Bush. Justice Thomas is the only member of the court who also took part in Bush v. Gore.

In response to Thursday’s hearing, President Trump told reporters that he believed his legal team prevailed. “I thought the presentation today was a very good one. I think it was well received,” he said. “I hope it was well received. You have millions of people that are out there wanting to vote, and they happen to want to vote for me or the Republican Party.”