WASHINGTON — Sen. Pat Toomey of Pennsylvania was one of seven Republicans who voted Saturday to convict former President Donald Trump of inciting the Jan. 6 insurrection at the Capitol, breaking with most of his party and likely closing the book on a winding and complicated relationship between the two.

Toomey, who is not seeking reelection when his term ends after 2022, was one of 57 total votes in favor of conviction, though that fell short of the two-thirds, or 67, needed to convict Trump, leading to his second impeachment acquittal.

But Toomey’s vote added to what was ultimately the most bipartisan Senate vote to convict a president in history, and amounted to a stark condemnation of a president he had supported.

“A lawless attempt to retain power by a president was one of the founders’ greatest fears,” Toomey said after the vote, later adding, “His betrayal of the Constitution and his oath of office required conviction.”

While Trump’s defense team argued there was no way to draw a line between his words and the deadly riot, Toomey held Trump directly responsible — both for spreading “dishonest” claims that he had won the election, and then stirring supporters to action.

“President Trump summoned thousands of people to Washington, D.C., inflamed their passions by repeating disproven allegations about widespread fraud,” Toomey said. “He urged that mob to march on the Capitol for the explicit purpose of preventing Congress and the vice president from formally certifying the results of the presidential election. He did all this to hold on to power despite having legitimately lost.”

Toomey’s stand stood in sharp contrast to that of most other Pennsylvania Republicans. Eight of the state’s nine GOP House members supported a challenge to the state’s electoral votes, and all nine opposed impeachment.

In a sign of a possible backlash at home to come, Pennsylvania GOP chairman Lawrence Tabas said he shared the “disappointment of many of our grassroots leaders and volunteers” over Toomey’s vote.

» READ MORE: First it was ‘fraud,’ then they just didn’t like the rules: How Pa. Republicans justified overturning an election

Every Senate Democrat voted to convict Trump, including Sen. Bob Casey of Pennsylvania and New Jersey Sens. Bob Mendez and Cory Booker.

Toomey was one of the few senators whose votes were unclear before Saturday’s roll call.

He voted for Trump twice, but signaled for weeks he was open to conviction, saying days after the riot that Trump “committed impeachable offenses.” He was one of six Republicans who voted to proceed with the trial, rejecting the argument that it is unconstitutional to try a former president.

But as a juror hearing evidence, he said little during the trial and hadn’t declared how he planned to vote on the impeachment article itself.

Over the years, Toomey supported the vast majority of Trump’s policies. But he also criticized some of the former president’s most incendiary conduct, and made clear his anger at the GOP attempt to throw out Pennsylvania’s election results.

Before the attack, Toomey delivered a point-by-point rebuttal of the push by Trump and other Republicans to nullify his state’s electoral votes. When the Capitol had been cleared and lawmakers returned, protected by security in tactical gear, Toomey directly blamed Trump.

“We saw bloodshed, because a demagogue chose to spread falsehoods and sow distrust of his own fellow Americans,” Toomey said that night on the Senate floor.

» READ MORE: Senate acquits Trump in his second impeachment trial, a coda to a tumultuous presidency

Toomey had also called for Trump to resign, much to the ire of some Pennsylvania Republicans, some who condemned Toomey for it — a contrast with the liberal critics who for years said he was too supportive of Trump.

Trump’s lawyers said that his speech was protected by the First Amendment, that the trial was unconstitutional, and that Democrats had engaged in equally inciting behavior while lusting after impeachment.

Toomey agreed that Trump had been badly treated by Democrats and the mainstream news media, and that there was a double standard applied to violent conduct on the left. But he said none of that justified Trump’s actions.

“I was one of the 74 million Americans who voted for President Trump, in part because of the many accomplishments of his administration,” Toomey said. “Unfortunately, his behavior after the election betrayed the confidence that millions of us had placed in him.”

Instead of being remembered for his accomplishments, Toomey added, Trump “will be remembered throughout history as the president who resorted to nonlegal steps to try to hold on to power.”

» READ MORE: Pat Toomey is ready to work with Joe Biden. A little.

Toomey has long had an uneven relationship with Trump. As he ran for reelection in 2016, Toomey ducked questions about whether he would support Trump until hours before polls closed on Election Day. He pledged to be “an independent voice.”

Once Trump was in office, Toomey sided with him often in the name of advancing conservative policies. He wrote much of Trump’s signature tax cuts and his attempt to repeal the Affordable Care Act, and backed the president’s push to appoint conservative judges. He voted with Trump’s position roughly 85% of the time, according to the website FiveThirtyEight. Toomey also opposed Trump’s first impeachment, saying the president had behaved inappropriately in pressuring Ukrainian leaders to smear Joe Biden but that his actions didn’t meet the high bar for removing a president from office.

But Toomey also criticized some of Trump’s personal conduct, including his equivocal response after neo-Nazis clashed with counterprotesters in Charlottesville, Va., in 2017, and a tweet urging four Democratic women of color to “go back” to the “crime infested places from which they came.”

The riot proved to be the final breaking point.