Senate Minority Leader Mitch McConnell told GOP colleagues in a letter that he will vote to acquit Donald Trump in the former president's impeachment trial, according to sources familiar with the communication.

McConnell's announcement ends a long period of silence over whether he would consider convicting Trump for incitement of insurrection and could pave the way for many other Republicans to follow in acquittal. The Kentuckian shared his decision in a note to fellow GOP senators on Saturday morning, ahead of what could be the final day of Trump’s second impeachment trial.

“While a close call, I am persuaded that impeachments are a tool primarily of removal and we therefore lack jurisdiction,” McConnell wrote.

That position puts McConnell in line with the votes he and 43 other GOP senators already cast, declaring Trump’s second trial unconstitutional. But the Republican leader, who has not spoken to Trump for weeks, suggested that criminal prosecution of the former president could be appropriate as a remedy following the violent Jan. 6 insurrection at the Capitol.

“The Constitution makes it perfectly clear that Presidential criminal misconduct while in office can be prosecuted after the President has left office, which in my view alleviates the otherwise troubling ‘January exception’ argument raised by the House,” McConnell wrote to fellow Republicans.

McConnell is not whipping colleagues on their votes, but the decision of the GOP leader to acquit Trump will certainly tamp down the number of "yes" votes. As many as 10 senators were thought to be considering a conviction vote as of Friday, but it's become harder and harder to see many senators convicting Trump other than the six who have voted to proceed.

Sens. Bill Cassidy of Louisiana, Susan Collins of Maine, Lisa Murkowski of Alaska, Pat Toomey of Pennsylvania, Ben Sasse of Nebraska and Mitt Romney of Utah voted that the trial is constitutional.

"Based on his comments over the past two months I really had no idea what he was going to do," said Sen. Roy Blunt (R-Mo.), a member of the GOP leadership team. “He said everybody should make this decision and their own and I guess he thought that that would apply to him as well."

McConnell has held his decision close throughout the trial, until Saturday, and said in his email that he continues to view the verdict as a “vote of conscience” but shared his choice because his colleagues have been directly asking how he’ll vote.

The Senate could take its final trial vote as soon as Saturday, although a burgeoning debate among Democrats over whether to make an eleventh-hour push for witnesses may yet prolong the proceedings.

Marianne LeVine contributed to this report.

Seven Republicans joined all 50 Democrats in voting to convict.

CBS News' senior White House and political correspondent Ed O'Keefe joins "CBS This Morning: Saturday" to talk about what can be expected as the impeachment trial of former President Trump draws closer to a vote, and if the Senate plans on calling witnesses.

Snow, frigid temperatures and freezing rain are expected to bring dangerous winter storms across the United States. Also, lawyers for former President Trump mounted their defense in his impeachment trial as the Senate draws closer to a final vote. All that and all that matters in today's Eye Opener. Your world in 90 seconds

The Senate voted on Saturday to acquit former President Donald Trump of inciting the deadly insurrection of Jan. 6, marking the close of an impeachment trial that laid bare the horrors of the riots and highlighted the country's halting efforts to extricate itself from the Trump era.

Most Senate Republicans sidestepped Democrats' central argument that Trump’s monthslong campaign to subvert the election results, as well as his incendiary remarks hours before a mob stormed the Capitol, demanded that he be convicted and barred from the presidency in the future. In the end, seven Republicans supported a conviction — 10 votes short of the two-thirds threshold required.

But even Senate Republicans leaders who voted to acquit Trump rebuked the former president, acknowledging that the House had proven its case and that Trump had violated his oath of office.

Senate Minority Leader Mitch McConnell (R-Ky.) said in a striking post-acquittal speech that Trump was “morally and practically responsible” for the Jan. 6 insurrection but he is “constitutionally not eligible for conviction” because he is no longer in office.

The 57-43 vote marked the first time since 1868 that a majority of the Senate voted to convict a president on an impeachment charge. And the seven Republicans who broke ranks are the most to support the conviction of a president from their own party in American history.

“The facts are clear,” said Sen. Richard Burr (R-N.C.), a retiring senator whose vote to convict nonetheless came as a surprise. "The evidence is compelling that President Trump is guilty of inciting an insurrection against a coequal branch of government and that the charge rises to the level of high crimes and misdemeanors.”

The outcome highlights Trump’s continued grip on the Republican Party, even after he left office facing withering condemnation from within the GOP for his post-election conduct. The Republican lawmakers who supported impeachment and conviction in the House and Senate have already faced sharp backlash from constituents and local GOP organizations.

The five-day impeachment trial, Trump’s second and by far the shortest in U.S. history, underscored the gaping contradictions of a post-Trump Washington — the intense desire among Democrats to punish Trump for his role in the violence, paired with their desire to pass a Covid-19 relief bill and turn the page on the Trump era. The urgency to expose every last detail of the forces that sparked the insurrection proved incompatible with the pressure to give President Joe Biden room to enact his agenda.

When the gavel fell, Republican Sens. Lisa Murkowski of Alaska, Ben Sasse of Nebraska, Pat Toomey of Pennsylvania, Bill Cassidy of Louisiana, Susan Collins of Maine, Mitt Romney of Utah, and Burr joined all Democrats in voting to convict Trump on the House’s single impeachment article.

“Let the record show — before God, history and the solemn oath that we swear to the Constitution — that there was only one correct verdict in this trial: Guilty,” Senate Majority Leader Chuck Schumer (D-N.Y.) said following the vote.

The trial ended with several unresolved mysteries that might be addressed in the coming weeks and could shed new light on Trump’s conduct. They include an ongoing effort to discern what Trump knew as the violence unfolded, when he knew it — and what actions, if any, he took to quell it.

Those questions dominated the final hours of the trial and nearly resulted in an effort by the House impeachment managers to open the process up to new testimony from witnesses. Several Republicans said in public statements that Trump had resisted pleas from allies to call off the rioters, and that he launched a Twitter attack on Vice President Mike Pence while he was being whisked from the Senate chamber.

Senate Democrats were blindsided on Saturday morning when the House impeachment managers sought witness testimony, resulting in a majority vote to call witnesses. But after negotiations among Democrats, the managers later relented and simply allowed a public statement from Rep. Jaime Herrera Beutler (R-Wash.) to be entered into the record. Herrera Beutler said in a statement late Friday evening that House Minority Leader Kevin McCarthy (R-Calif.) had told her that Trump denied his pleas to forcefully call off the rioters on Jan. 6, setting off immediate calls for a more thorough airing of the evidence against the former president.

The decision to skip live testimony left those details unconfirmed and poised to emerge after Trump is free of the trial.

Democrats had expressed hope that the evidence and the emotional appeals they made during the trial would move enough Republicans to convict Trump — a result they said was necessary to ward off future violence. To make their case, the House managers played graphic videos, including never-before-seen-footage, showing the horrifying and chaotic nature of the violence at the Capitol on Jan. 6.

Trump’s defense team maintained that putting a former president on trial on impeachment charges was unconstitutional because the primary remedy, removal from office, was no longer operative. But the Senate voted at the start of the trial to uphold the chamber’s authority to have the proceedings, and a conviction would have barred Trump from holding future federal office.

The argument from Trump’s lawyers, a minority view among constitutional experts, provided an avenue for Republicans to coalesce around an acquittal without explicitly defending Trump’s conduct, which most GOP senators have criticized as reckless but not impeachable.

Other Republicans said the House had failed to prove that Trump’s actions and remarks contributed to the violence at the Capitol, and that it did not meet the legal standard for incitement.

McConnell, despite his vote to acquit Trump, lashed the former president in a statement after the trial, accusing him of being responsible for unleashing “terrorism” on the Capitol.

“They did this because they’d been fed wild falsehoods by the most powerful man on Earth because he was angry he lost an election,” McConnell said. “Many politicians sometimes make overheated comments … but that was different. That’s different from what we saw. This was an intensifying crescendo of conspiracy theories.”

Notably, McConnell also suggested that Trump might still face criminal liability for his actions, contending that Trump “didn't get away with anything yet.”

Michael van der Veen, one of Trump’s attorneys for the impeachment trial, dismissed McConnell’s criticisms, telling reporters: “We finished the grappling in that room and we slammed it down on the mat on this case. We won. Not guilty.”

Lawmakers said the case against Trump was overwhelming; they argued that the rioters heeded his words, acted upon them, repeated them while storming the Capitol and then cited them in court when they faced prosecution.

In addition, senators who voted to punish Trump cited his failure to send help to the Capitol until hours after it became clear that Congress had been overtaken by the violent insurrection and that Pence was in danger and had been evacuated from the Senate chamber.

The House managers and Trump’s lawyers clinched an agreement to avoid witness testimony after both sides agreed to enter a public statement from Herrera Beutler that detailed her account of a phone call between Trump and McCarthy.

Herrera Beutler, who voted to impeach Trump in the House, pleaded with Pence and other Republicans to publicly tell their story — but by Saturday afternoon, as the acquittal vote neared, no others had stepped forward.

The House managers said the call was evidence that Trump violated his oath of office and showed no remorse even as he was told that violent rioters have overtaken the building.

Pence was at the Capitol on that day to preside over a joint session to certify Biden’s Electoral College victory. Trump had spent months priming his supporters to believe the election was rigged and stolen, and as his post-election attempts to flip the results repeatedly failed, his efforts became more destabilizing.

By late December, Trump was calling for his supporters to descend on the nation’s capital for a “wild” rally. Law enforcement and intelligence officials warned that elements of the rally-goers would likely be armed and present a threat of violence. But that day, Trump addressed the crowd and urged them to march on the Capitol and “fight like hell” to stop the counting of electoral votes — or else risk losing their country.

Many of the rioters themselves posted on social media and sent messages since recovered by law enforcement indicating they were awaiting Trump’s signal before acting.

But Trump’s team said he had also urged his supporters to go “peacefully.” They said Trump was initially “horrified” by the violence and took immediate steps to respond to it, but did not provide evidence to support those contentions. The defense team presented for just a few of the 16 hours they were allotted, a move that kept the trial to just a five-day affair.

As they rested their case against Trump on Saturday, the House managers made one final plea to senators.

“Our reputations and our legacy,” said Rep. Jamie Raskin (D-Md.) the House’s lead impeachment manager, “will be inextricably defined by what we do here.”