Trump impeachment trial live updates: Biden says charge 'not in dispute' in 1st comments on acquittal

Trump's second impeachment trial -- the first for a former president -- resumes Wednesday at noon with opening arguments from House impeachment managers who will begin making their case that Trump incited an insurrection.

They have up to 16 hours to convince 17 Republicans to join the Democrats in voting to convict Trump and bar him from federal office. To compel senators, and the American public, they are expected to use "never-seen-before" video footage of the attack, aides to the House impeachment managers said.

On Tuesday, the group, led by Rep. Jamie Raskin, D-Md., presented a 13-minute montage video of the Jan. 6 attack on the Capitol, interspersed with Trump's remarks at the rally outside the White House, and argued acquitting Trump would allow a "January exception" to the Constitution not intended by the Framers. 

Trump's defense team argued that the trial was unconstitutional because Trump is now a private citizen and that moving forward would encourage "snap impeachments." However, lead attorney, Bruce Castor, first setting the tone for the trial, spent most of his 48 minutes on the Senate floor meandering through topics that weren't related to the constitutional questions facing the Senate.

Trump, watching from Mar-a-Lago, was unhappy with Castor's performance, sources told ABC News.

After the first day's arguments, in an unexpected move, Sen. Bill Cassidy, R-La., joined Democrats and five other Republicans in voting that the trial is constitutional, changing his vote from an earlier motion on the issue, citing the Democrats' "compelling argument."

John Cornyn, R-Texas, and other Republicans also criticized the performance of Trump's legal team, but the majority of Republicans, 44-56, voted not to move forward with the proceedings, signaling it's all but certain Democrats won't have the votes to convict Trump. At Trump's impeachment trial last year, only one Republican, Sen. Mitt Romney of Utah, voted with Democrats.

The district attorney's office in Fulton County, Georgia, has formally launched a criminal probe into Trump's efforts to overturn his election loss in the state, after Trump was heard in a January phone call pleading with Secretary of State Brad Raffensperger to help him "find 11,780 votes," the exact number he needed to win Georgia.

The launching of the investigation was revealed in a letter from District Attorney Fani Willis to state officials asking them to preserve any documents potentially related to the 2020 general election, "with particular care given to set aside and preserve those that may be evidence of attempts to influence the actions of persons who were administering" it, which would include Trump's Jan. 2 phone call with the secretary. The existence of the letter was first reported by the New York Times and obtained by ABC News.

"This investigation includes, but is not limited to, potential violations of Georgia law prohibiting the solicitation of election fraud, the making of false statements to state and local governmental bodies, conspiracy, racketeering, violation of oath of office and any involvement in violence or threats related to the election's administration," Willis writes in the letter.

Senior aides to the House impeachment managers said they plan to show "never before seen" security camera footage offering a view of the Capitol during the Jan. 6 riot "that has never been published before."

"We have the goods, we will be presenting the goods," said a senior aide.

When asked about whether they had body camera footage from law enforcement, aides dodged the specifics, but said it would provide "new insight into the extreme violence and risk" people faced on Jan. 6.

They plan to try the case against Trump like a criminal prosecution with "a beginning, middle and an end." 

"The Trump team really has one strategy, and that is to talk about anything and everything else, besides the President's actions on that day in the lead up," an aide said. 

-ABC News' Rachel Scott, Benjamin Siegel, Katherine Faulders, Trish Turner, Mariam Khan and Allison Pecorin

Rep. Adam Kinzinger, R-Ill., who voted in the House to impeach President Donald Trump, told ABC News Live Prime anchor Linsey Davis that he believes it is possible, but not likely, that more Senate Republicans will vote to convict Trump. Kinzinger estimates there will not be enough to get to 67 votes, though he also said if the Senate impeachment vote was held in private, he believes it would "certainly" pass.

"I think over time, people are going to wake up to really how bad, at least, the tone was in the last four years, particularly Jan. 6, and I don't think history is going to judge too kindly those that stood by and picked politics over that oath-keeping decision," Kinzinger said.

The Republican congressman also discussed the future of the GOP and said that if the party continues to go in the direction he feels it's going in, he wouldn't be able to "stay under the Republican banner."

"I'm determined to fight for my party, but if it continues down this track, and there's no hope for it. I certainly wouldn't be able to stay under the Republican banner as much as I want to, you know, I need to be associated with a party that's optimistic about the future," Kinzinger said. "And I'm not there yet. I'm going to fight for the soul of this party and down the road, hopefully, that won't be a decision I'll have to make."

-ABC News' Jon Schlosberg