45 Senate Republicans voted to declare Trump's impeachment trial unconstitutional, all but guaranteeing his acquittal

• Forty-five Senate Republicans voted Tuesday to declare Trump's impeachment trial unconstitutional.
• Only five Republican senators voted against the motion.
• The development all but guarantees Trump's eventual acquittal following the trial.

Forty-five Senate Republicans voted to declare former President Donald Trump's impeachment trial unconstitutional on Tuesday, all but securing his eventual acquittal.

The vote came minutes after US senators were sworn in as jurors in the trial, when Kentucky Sen. Rand Paul raised a point of order forcing the chamber to decide on the constitutionality of even holding a trial in the first place. The point of order ultimately failed, with 55 senators voting to kill it and 45 voting to uphold it.

Only five Republican senators - Susan Collins, Lisa Murkowski, Mitt Romney, Ben Sasse, and Pat Toomey - voted against Paul's motion. Notably, Senate Minority Leader Mitch McConnell came out in favor of Paul's point of order, indicating how he thought his caucus should vote on convicting Trump. McConnell had previously refused to say how he'd vote in the trial.

Multiple Republican lawmakers have pushed the theory in recent days that holding an impeachment trial for Trump runs afoul of the Constitution because he has already left the White House. Some legal scholars expressed support for the notion, but most have dismissed it and said refusing to hold an impeachment trial for a federal official because they were about to leave office or had already left office would allow them to escape accountability.

"That makes no sense at all," the Yale Law School professor Akhil Reed Amar told NPR, referring to the GOP's argument. "You want to give someone a get-out-of-jail free card at the end of the administration so they can do anything they like and be immune from the high court of impeachment?"

Over lunch on Tuesday, the conservative constitutional law professor Jonathan Turley briefed Republicans and argued that holding an impeachment trial for a former official was unconstitutional. But there is precedent for such an act. In 1876, the House impeached Secretary of War William Belknap after he resigned, and the Senate subsequently held a trial.

But there is scant appetite within the Republican caucus to hold an impeachment trial, let alone convict Trump after the House charged him with "incitement of insurrection" related to the deadly Capitol siege on January 6.

"There aren't many in the Republican conference that I've talked to that are leaning towards it being constitutional," Sen. Mike Braun of Indiana told Insider before the vote on Tuesday. "It sounds a little bit after the fact when somebody's gone from office when that's the whole point of impeachment. But again, I'm going to listen to anything that might say otherwise between now and when we're required to vote one way or the other."

Braun voted to uphold Paul's point of order declaring the trial unconstitutional.

South Dakota Sen. Mike Rounds also signaled his position on the impeachment trial, shaking his head when asked if he believed it was constitutional. He also sided with Paul.

Texas Sen. Ted Cruz, one of Trump's most stalwart defenders in Congress and a leading voice in the charge to overturn the election results in battleground states Trump lost, told Insider before the vote that he believed the question of constitutionality was a "close" one.

"There's an open question on whether or not a former office holder is subject to impeachment," he said. "There are serious legal scholars on both sides of the question. Constitutional text - there is language that can be read either way. I think it's a close question."

Even so, holding an impeachment trial for Trump is a "mistake," Cruz added.

"President Trump has already left office. We have a new administration," he said. "I think this impeachment trial is petty, it is vindictive, and I think it's time to move on."

Cruz voted with most of his caucus to declare the trial unconstitutional.

North Carolina Sen. Richard Burr didn't initially say whether he believed Trump's impeachment trial was constitutional. But he also later voted in favor of Paul's motion.

Support from two-thirds of the Senate is required to convict Trump. Democrats have a bare majority in the chamber - 50 seats plus Vice President Kamala Harris' tiebreaking vote - which means at least 17 Republicans would have to break ranks for Trump to be convicted and potentially barred from ever running for public office again.

Even if the five Republicans who voted to table Paul's motion on Tuesday also voted to convict Trump, it's unlikely they'd be joined by a dozen of their colleagues who declared the process itself unconstitutional.

Paul said earlier Tuesday that he believed enough Republicans would side with him and "show there's no chance they can impeach the president."

"If 34 people support my resolution that this is an unconstitutional proceeding, it shows they don't have the votes and we're basically wasting our time," he said, adding that a trial would be "dead on arrival" if he got more than 34 votes.