Romney was the only GOP senator to vote in support of removing Trump from office, drawing praise from critics of the president and backlash from fellow Republicans.
The two figures have had a tumultuous relationship for years, feuding well before Trump became president and Romney entered the Senate.
Here’s a look at their fractious relationship:
Feb. 2, 2012: Trump endorses Romney’s White House bid
Trump endorsed Romney in his 2012 presidential campaign, calling him “tough” and “smart” while appearing alongside the former Massachusetts governor.
“He’s not going to continue to allow bad things to happen to this country,” Trump said.
Romney later praised Trump’s “extraordinary ability to understand how our economy works” and for being “one of the few who has stood up to say China is cheating” on trade.
Nov. 7, 2012: Trump remarks on Romney’s failed electoral bid
After former President Obama won reelection, Trump tweeted that Romney “is a good man but he just never connected with the people.”
He had sent tweets months before the election boosting Romney and touting his White House campaign.
Oct. 15, 2014: Trump says Romney shouldn’t run again
A year before launching his own campaign, Trump spoke out against speculation of Romney launching a third White House bid in 2016.
“I can’t believe that Mitt Romney would run for president again. He had his chance and blew it in the last weeks of the race,” Trump tweeted.
July 8, 2015: Romney criticizes Trump’s early White House campaign
Romney hit Trump about a month after he announced his campaign, condemning his comments about Mexican immigrants entering the U.S.
He also spoke out after Trump went after Sen. John McCain‘s (R-Ariz.) military record.
“The difference between @SenJohnMcCain and @realDonaldTrump: Trump shot himself down. McCain and American veterans are true heroes,” Romney tweeted.
“Why would anybody listen to @MittRomney?” Trump responded, saying Romney “lost an election that should have easily been won.”
Sept. 30, 2015: Romney predicts a Trump loss; Trump says he ‘choked’
Romney predicted that Trump would not win the GOP nomination, saying his party has “historically nominated someone who’s a mainstream conservative and someone who has a foundation in foreign policy.”
Trump responded on Twitter, knocking the former governor for losing to Obama. “Should’ve won — he choked!” Trump tweeted.
Oct. 16, 2015: Romney criticizes Trump’s ‘childish’ comments
Romney remarked in an interview that Trump, then the front-runner in the GOP presidential primary, could be hurting his chances in 2016 with his “childish” remarks.
“I think Donald Trump has said a number of things which are hurtful, and he has said they were childish in some respects, and I think will be potentially problematic either in a primary or in a general election if he were to become the nominee,” he said.
Feb. 25, 2016: Trump calls Romney ‘one of the dumbest’ candidates in history of GOP
After Romney called on Trump to release his taxes, Trump pushed back on Twitter, calling Romney “one of the dumbest and worst candidates in the history of Republican politics.”
March 3, 2016: Romney makes last-ditch appeal against ‘phony’ and ‘fraud’ Trump
Several months before Trump became the Republican Party’s presidential nominee, Romney slammed the candidate in a speech that went after his business experience.
“Here’s what I know: Donald Trump is a phony, a fraud,” Romney said. “His promises are as worthless as a degree from Trump University. He’s playing members of the American public for suckers: He gets a free ride to the White House, and all we get is a lousy hat.”
Hours after Romney’s speech, Trump tweeted, “Why did Mitt Romney BEG me for my endorsement four years ago?”
Romney also said that month that if Trump had said the things he said about “the KKK, Muslims, Mexicans, disabled,” he would “NOT have accepted his endorsement” in 2012.
May 25, 2016: Trump says Romney ‘choked like a dog’
During a rally, Trump criticized Romney along with a handful of prominent Republican figures.
He again criticized Romney for not winning the presidency, saying the former governor “choked like a dog. He’s a choker.”
Nov. 9, 2016: Romney congratulates Trump on winning
Romney offered support for Trump after his 2016 win.
“Best wishes for our duly elected president: May his victory speech be his guide and preserving the Republic his aim,” Romney tweeted.
A few days later, Trump tweeted that Romney called to congratulate him, calling it “very nice.”
Nov. 29, 2016: Trump meets with Romney, considers him for secretary of State
As president-elect, Trump said he was considering picking Romney as his secretary of State, despite the pair’s rocky history.
Romney dined with Trump as the president-elect weighed his Cabinet picks, with the former governor saying he and Trump had a “wonderful evening.”
Trump later said in an interview on the “Today Show” when he was announced as Time magazine’s Person of the Year that he and Romney had “come a long way.”
“It’s not about revenge, it’s about what’s good for the country, and I’m able to put this stuff behind us,” he added.
Dec. 13, 2016: Trump picks Tillerson to lead State Department
Trump announced he selected Exxon Mobil CEO Rex Tillerson as his nominee for secretary of State over Romney and other prominent Republicans he was reportedly considering.
Aug. 18, 2017: Romney rebukes Trump’s Charlottesville remarks
Romney strongly rebuked Trump’s remarks after the president said there were “very fine people on both sides” after a violent white supremacist rally in Virginia.
“His apologists strain to explain that he didn’t mean what we heard. But what we heard is now the reality, and unless it is addressed by the president as such, with unprecedented candor and strength, there may commence an unraveling of our national fabric,” Romney said in a statement.
Dec. 4, 2017: Trump urges Hatch to run for reelection amid speculation of a Romney bid
Dec. 6, 2017: Conway says Trump and Romney have a ‘great relationship’
White House counselor Kellyanne Conway told CNN that Trump and Romney had a “great relationship.”
“The President and Gov. Romney spoke, I don’t know, 10 hours ago, less than 12 hours ago, and people should know that because otherwise there’s speculation,” Conway said after Trump made a trip to Romney’s home state of Utah.
Jan. 2, 2018: Hatch announces retirement, clearing path for Romney run
Hatch announced he would be retiring at the end of his term, clearing the path for Romney to seek his Senate seat.
Feb. 19, 2018: Trump endorses Romney for Senate
Trump backed Romney in the Senate race to replace Hatch, after reports that the president had urged retiring Hatch to run for reelection to block a Romney bid.
Trump tweeted that Romney is a “worthy successor” to Hatch and had his “full support and endorsement.”
Romney accepted the endorsement and thanked Trump for his support.
May 1, 2018: Romney praises Trump’s first year in office
Romney praised Trump’s first year in office, saying that it was similar to what he would have done if elected.
“The things he’s actually done have been better than I expected,” Romney said.
June 24, 2018: Romney says he’ll speak out against Trump on ‘substantial’ issues
Romney, in an op-ed for The Salt Lake Tribune, said he would continue to speak out against Trump “only” when he believes “it is a matter of substantial significance.”
The next month he said it was “too early” to say whether he would support Trump in 2020.
July 16, 2018: Romney rips Trump’s ‘disgraceful’ comments at Putin summit
Romney said it was “disgraceful and detrimental to our democratic principles” for Trump to question U.S. intelligence agencies’ assessment that Russia interfered in the 2016 election while at a joint news conference with Russian President Vladimir Putin in Finland.
“President Trump’s decision to side with Putin over American intelligence agencies is disgraceful and detrimental to our democratic principles,” Romney said.
Nov. 6, 2018: Romney wins Senate race
Romney won his race to fill Hatch’s Senate seat, securing more than 60 percent of the vote.
March 19, 2019: Romney hits Trump for McCain criticism
Romney again criticized Trump for going after the late Sen. John McCain (R-Ariz.), after Trump said that he “was never a fan of John McCain, and I never will be.”
“I can’t understand why the President would, once again, disparage a man as exemplary as my friend John McCain: heroic, courageous, patriotic, honorable, self-effacing, self-sacrificing, empathetic, and driven by duty to family, country, and God,” Romney tweeted.
Jan. 2, 2019: Romney says he won’t challenge Trump in 2020 but doesn’t back him
Romney said he would not mount a primary challenge against Trump in the 2020 election, but did not go so far as to back the president in the race.
His announcement came a day after he published an op-ed in The Washington Post criticizing Trump for his lack of character and moral leadership.
April 19, 2019: Romney said he’s ‘sickened’ by Trump’s behavior in Mueller report
Romney said he was “sickened at the extent and pervasiveness of dishonesty and misdirection by individuals in the highest office of the land, including the president,” after former special counsel Robert Mueller’s 448-page report was released.
Trump repeatedly slammed the report in an effort to discredit Mueller and his findings.
Oct. 5, 2019: Trump calls for Romney’s impeachment
Trump called for Romney to be impeached and said he made a mistake in endorsing him for his Senate seat.
Senators cannot be impeached but can face recall votes in some states, however Utah does not have any provisions in state law for recalling a sitting senator.
The same day, Trump called Romney a “pompous ass” over the senator’s criticism of his dealings with Ukraine.
“Somebody please wake up Mitt Romney and tell him that my conversation with the Ukrainian President was a congenial and very appropriate one,” Trump tweeted.
“Mitt Romney never knew how to win. He is a pompous ‘ass’ who has been fighting me from the beginning, except when he begged me for my endorsement for his Senate run (I gave it to him), and when he begged me to be Secretary of State (I didn’t give it to him). He is so bad for R’s!” Trump added in another tweet.
Oct. 17, 2019: Romney calls Trump’s deal to withdraw troops from Syria ‘a bloodstain’ in US history
Romney ripped the Trump administration’s cease-fire deal in Syria after the president decided to withdraw troops from the region, paving the way for a Turkish invasion.
“The announcement today is being portrayed as a victory. It is far from a victory. Serious questions remain about how the decision was reached precipitously to withdraw from Syria and why that decision was reached,” Romney said in a Senate floor speech.
He said the announced cease-fire did not change the fact that the U.S. “abandoned” the Kurdish forces, saying, “What we have done to the Kurds will stand as a bloodstain in the annals of American history.”
Oct. 18, 2019: Trump tweets ad hitting Romney as ‘Democrat secret asset’
Trump tweeted an ad from the group Club for Growth that called Romney a “Democrat secret asset” amid the senator’s criticism of Trump’s dealings with Ukraine, the issue at the center of impeachment proceedings.
“REPUBLICANS MUST STICK TOGETHER AND FIGHT!” Trump tweeted.
Nov. 21, 2019: Romney calls lunch with Trump ‘delightful’
Despite their escalating feud, Romney joined other GOP senators for a lunch with Trump at the White House, which Romney later described as “delightful.”
The two shook hands at the lunch and Romney said there didn’t appear to be any signs of lingering tension between them.
Jan. 31: Romney supports witnesses for impeachment trial
A Romney official confirmed that the Utah senator would be voting to allow additional witnesses and documents in the impeachment trial.
He was one of only two Senate Republicans, along with Sen. Susan Collins (Maine.), to vote in favor of the measure, which was supported by all Senate Democrats.
As Romney “has said, he wants to hear from Ambassador [John] Bolton, and he will vote in favor of the motion today to consider witnesses,” Romney spokeswoman Liz Johnson tweeted before the vote.
Feb. 5: Romney breaks from GOP, votes to convict Trump
Romney announced hours before the impeachment saga came to an end that he would be voting to convict Trump on the charge of abuse of power.
“The president is guilty of an appalling abuse of public trust. What he did was not perfect. No, it was a flagrant assault of our electoral rights, our national security and our fundamental values,” Romney said on the Senate floor.
“I swore an oath before God to exercise impartial justice. I am profoundly religious. My faith is at the heart of who I am. I take an oath before God as enormously consequential,” Romney, a devout Mormon, added.
The GOP senator, however, voted with his party to acquit Trump on the charge of obstruction of Congress.
Feb. 6: Trump hits Romney as a ‘failed presidential candidate’
Trump hit back at Romney in an early morning tweet after his vote against him in the impeachment trial.
“Had failed presidential candidate @MittRomney devoted the same energy and anger to defeating a faltering Barack Obama as he sanctimoniously does to me, he could have won the election,” Trump tweeted.
Later in the day, speaking at the National Prayer breakfast, the president again swiped at Romney over his vote.
The president called out politicians who “use their faith as justification for doing what they know is wrong.”
“Weeks ago, and again yesterday, courageous Republican politicians and leaders had the wisdom, fortitude and strength to do what everyone knows was right,” Trump said. “I don’t like people who use their faith as justification for doing what they know is wrong.”