WASHINGTON -- In his speech from the Senate floor, Sen. Mitch McConnell delivered a scalding denunciation of Donald Trump, calling him "morally responsible" for the Jan. 6 attack on the U.S. Capitol.

But earlier Saturday in his vote on Trump's impeachment, McConnell said "not guilty" because he said a former president could not face trial in the Senate.

Washington's most powerful Republican and the Senate's minority leader used his strongest language to date to excoriate Trump minutes after the Senate acquitted the former president, voting 57-43 to convict him but falling short of the two-thirds majority needed to find him guilty. Seven Republicans voted to convict.

Clearly angry, the Senate's longest-serving GOP leader said Trump's actions surrounding the attack on Congress were "a disgraceful, disgraceful dereliction of duty." He even noted that though Trump is now out of office, he remains subject to the country's criminal and civil laws.

"He didn't get away with anything yet," said McConnell, who turns 79 next Saturday and has led the Senate GOP since 2007.

It was a stunningly bitter castigation of Trump by McConnell, who could have used much of the same speech had he instead decided to convict Trump.

But by voting for acquittal, McConnell and his fellow Republicans left the party locked in its struggle to define itself after Trump's defeat in November. Fiercely loyal pro-Trump Republicans, and the base of the party they represent, are colliding with more traditional Republicans who believe the former president is damaging the party's national appeal.

"It was powerful to hear the 57 guilties and then it was puzzling to hear and see Mitch McConnell stand and say not guilty and then minutes later stand again and say he was guilty of everything," one of the House prosecutors, Rep. Madeleine Dean, D-Pa., said Sunday on ABC's "This Week." "History will remember that statement of speaking out of two sides of his mouth."

A guilty vote by McConnell, which likely would have brought some other Republicans along with him, would have marked a more direct effort to wrest the party away from Trump.

That could have prompted 2022 primary challenges against GOP incumbents, complicating Republican efforts to win the Senate majority by nominating far-right, less-electable candidates. McConnell has spent years fending off such candidates.

"Time is going to take care of that some way or another," said Sen. Chuck Grassley, R-Iowa, asked about the party's course. "But remember, in order to be a leader you got to have followers. So we're gonna find out."

After Saturday's vote, furious Democrats launched their own attacks against McConnell and the GOP. Speaking to reporters, House Speaker Nancy Pelosi, D-Calif., mocked the "cowardly group of Republicans" in the Senate she said were afraid to "respect the institution in which they served."

She also said McConnell had created a self-fulfilling prophecy, forcing the Senate trial to begin after Trump left the White House by keeping the chamber out of session. Republicans say Pelosi could have triggered the proceedings earlier by delivering official impeachment documents sooner.

McConnell had signalled last month that he was open to finding Trump guilty, a jaw-dropping admission of alienation after spending four years largely helping him or ducking comments about his most outrageous assertions. McConnell informed GOP senators how he would vote in a private email early Saturday, saying, "While a close call, I am persuaded that impeachments are a tool primarily of removal and we therefore lack jurisdiction."

He expanded on his rationale on the Senate floor after Saturday's roll call, making clear his enmity toward Trump's actions.

"There is no question, none, that President Trump is practically and morally responsible for provoking the event of that day," he said.

Even before the November election, Trump repeatedly claimed that if he lost it would be due to fraud by Democrats, a false accusation that he continued to assert until leaving office.

He summoned supporters to Washington for Jan. 6, the day Congress would formally certify his Electoral College loss to Joe Biden, then used a provocative speech near the White House to urge them to march on the Capitol as that count was underway. His backers violently fought past police and into the building, forcing lawmakers to flee, temporarily disrupting the vote count and producing five deaths. The visceral, bloody images from that day were at the core of Democrats impeachment case against Trump.

McConnell called that assault a "foreseeable consequence" of Trump using the presidency, calling it "the largest megaphone on Planet Earth." Rather than calling off the rioters, McConnell accused Trump of "praising the criminals" and seeming determined to overturn the election "or else torch our institutions on the way out."

The 36-year Senate veteran manoeuvred through Trump's four years in office like a captain steering a ship through a rocky strait on stormy seas. Battered at times by vindictive presidential tweets, McConnell made a habit of saying nothing about many of Trump's outrageous comments.

He ended up guiding the Senate to victories such as the 2017 tax cuts and the confirmations of three Supreme Court justices and more than 200 other federal judges.

Their relationship, built more on expedience than admiration, plummeted after Trump's denial of his Nov. 3 defeat and relentless efforts to reverse the voters' verdict with his baseless claims that Democrats fraudulently stole the election.

It withered completely last month, after Republicans lost Senate control with two Georgia runoff defeats they blamed on Trump, and the savage attack on the Capitol by Trump supporters. The day of the riot, McConnell railed against "thugs, mobs, or threats" and described the attack as "this failed insurrection."

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Associated Press writers Mary Clare Jalonick and Lisa Mascaro contributed to this report.