Sen. Mitt Romney Willard (Mitt) Mitt RomneyThe Memo: Warning signs flash for Trump on debates GOP votes to authorize subpoenas, depositions in Obama-era probe Overnight Defense: Trump hosts Israel, UAE, Bahrain for historic signing l Air Force reveals it secretly built and flew new fighter jet l Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' MORE (R-Utah) shocked his fellow Republican senators and surprised much of the nation on Wednesday with a dramatic floor speech announcing he would vote to convict President Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE on the impeachment charge of abuse of power.

Romney announced his decision in a nearly empty Senate chamber just hours before the Senate voted to acquit Trump and after fellow GOP colleagues such as Sens. Susan Collins Susan Margaret CollinsThe Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally Gideon leads Collins by 12 points in Maine Senate race: poll Senate leaders quash talk of rank-and-file COVID-19 deal MORE (Maine) and Lisa Murkowski Lisa Ann MurkowskiGOP ramps up attacks on Democrats over talk of nixing filibuster OVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' House Democrats tee up vote on climate-focused energy bill next week MORE (Alaska) had already announced they would not vote to convict Trump.

Just as surprising as his vote was the intensity of the 2012 Republican presidential nominee’s language.

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While other Senate Republicans chided Trump for “inappropriate” conduct, Romney said “the president is guilty of an appalling abuse of public trust” and “a flagrant assault on our electoral rights.”

“The grave question the Constitution tasks senators to answer is whether the president committed an act so extreme and egregious that it rises to the level of a ‘high crime and misdemeanor.’ Yes, he did,” he said.

Romney, however, voted against the second article of impeachment accusing the president of obstruction of Congress, which failed along strict party lines.

Senate Republicans along with most of the rest of the political world thought Trump would be acquitted on a straight party-line vote after Collins, who faces a tough reelection race this year in a state carried by Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Virginia Democrat blasts Trump's 'appalling' remark about COVID-19 deaths in 'blue states' The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE in 2016, said she would vote against conviction.

If anything, it appeared more likely that Democrats would suffer defections.

Instead, Democrats won a key talking point from Romney’s vote, which they will surely use in the weeks and months to come.

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Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE (R-Ky.) after the vote said he had hoped to replicate the unanimous Republican vote against the articles that GOP leaders mustered in the House.

He said he was “surprised” and “disappointed” by Romney’s vote, indicating he received little if any advance warning.

Still, he tried to downplay the defection.

“I think they’re pretty clearly party lines both ways. I think that’s what you can take out of it, pretty much party line in both chambers,” he said when asked to assess the final Senate and House votes.

Democrats were elated by Romney’s announcement.

Sen. Richard Blumenthal (D-Conn.) called his vote “momentous,” while Sen. Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (D-Colo.) said it “restores my faith in democracy.”

Republicans were caught off guard, though GOP senators, for the most part, didn’t lace into Romney.

“I am surprised,” said Sen. Josh Hawley Joshua (Josh) David HawleyWhat Facebook's planned change to its terms of service means for the Section 230 debate Republican Senators raise concerns over Oracle-TikTok deal TikTok, Oracle seek Trump's approval as clock ticks down MORE (R-Mo.), one of the president’s most ardent Senate defenders. Sen. Ted Cruz Rafael (Ted) Edward CruzLoeffler calls for hearing in wake of Netflix's 'Cuties' Health care in the crosshairs with new Trump Supreme Court list 'Parks and Rec' cast members hosting special reunion to raise money for Wisconsin Democrats MORE (R-Texas), another staunch Trump ally, said, “I disagree with his decision. I think it’s a mistake.”

In a statement, the White House described Romney as a “failed Republican presidential candidate,” and Donald Trump Jr. called on the Senate GOP to expel Romney from its conference.

The White House press office abruptly canceled a press availability for Trump and Venezuela’s opposition leader, Juan Guaidó, that was scheduled to take place in the Oval Office minutes after Romney announced his decision. It did not offer an explanation for the move, stirring speculation that officials were caught off guard by the news.

A Republican senator who requested anonymity to comment on Romney’s vote said he was “disappointed” but didn’t want to add any fuel to the fire by bashing his colleague.

The person most impacted by Romney’s vote may be Collins, who has been running ads in Maine stressing her brand as an independent.

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By breaking with Republicans on what could be the most defining vote of his career, Romney has set a new standard for independence for GOP lawmakers, who have been reluctant to forcefully challenge the president during his first three years in office.

“It puts Sen. Collins in a real bad spot to have someone run in that independent [lane] that she typically does. This is such a tough vote for her,” said a Senate Republican aide.

Collins later told reporters, “Every senator has to make his own decision. I don’t agree with Mitt’s decision.”

But when asked if Romney should be punished with expulsion from the conference, Collins said, “Of course not.”

Romney said he fully expected to be “denounced” for breaking with his party on such a politically charged vote but that he felt compelled to vote according to his conscience and moral values.

The Utah senator paused for several seconds and looked down at his desk, appearing to choke up with emotion, at the start of his speech, the first sign that he was about to drop a bombshell on the Senate floor.

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“I am a profoundly religious person. I take an oath before God as enormously consequential. I knew from the outset that being tasked with judging the president, the leader of my own party, would be the most difficult decision I have ever faced,” he said.

His vote could give momentum for a bill introduced by Utah state Rep. Tim Quinn (R) that would allow voters to recall a U.S. senator with a ballot measure.

A Senate Republican aide, however, dismissed the legislation as an unconstitutional infringement on federal power.

Asked how long Romney would be in the doghouse, McConnell said, “We don’t have any doghouses here. The most important vote is the next vote.”

Other Republicans flatly rejected the idea of kicking Romney out of the conference or stripping him of his committee assignments.

Sen. Mike Braun Michael BraunPessimism grows as hopes fade for coronavirus deal McConnell shores up GOP support for coronavirus package Patient Protection Pledge offers price transparency MORE (R-Ind.) waved off talk of expelling Romney from the conference as “silly talk.”

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Other Republicans urged tolerance for different points of view.

Sen. Lamar Alexander Andrew (Lamar) Lamar AlexanderTrump health officials grilled over reports of politics in COVID-19 response Now is the time to renew our focus on students and their futures CDC says asymptomatic people don't need testing, draws criticism from experts MORE (R-Tenn.) said “every senator has a right to vote how he or she feels,” while Sen. Richard Shelby Richard Craig ShelbyDems discussing government funding bill into February GOP short of votes on Trump's controversial Fed pick This week: House returns for pre-election sprint MORE (R-Ala.), one of the Senate’s most senior lawmakers, said “the party ought to be a big umbrella.”

Jordain Carney, Morgan Chalfant and Brett Samuels contributed.