Sen. Mitt Romney, R-Utah, is bracing for "unimaginable" consequences as President Donald Trump and his allies seek revenge over his impeachment vote.

Romney was the sole Republican to vote for Trump's conviction Wednesday. His vote did little to change the all-but-guaranteed end to the president's impeachment trial — acquittal — but it dramatically shifted the surrounding narrative. An impeachment process that Trump had called entirely "partisan" no longer was so.

As Democrats praised Romney for his act of "moral courage," Trump world began relentlessly attacking him.

Trump said at Thursday morning's National Prayer Breakfast that "I don't like people who use their faith as justification for doing what they know is wrong."

His comments were a thinly veiled shot at Romney, who cited his Mormon beliefs during his speech announcing his impeachment vote.

"I swore an oath before God to exercise impartial justice," Romney said from the Senate floor Wednesday. "I am profoundly religious. My faith is at the heart of who I am."

Wednesday, the president tweeted an ad depicting Romney as a Democratic "secret asset." Recalling Romney's loss to President Barack Obama in the 2012 presidential election, Trump tweeted early Thursday that if the "failed presidential candidate" had "devoted the same energy and anger to defeating a faltering Barack Obama as he sanctimoniously does to me, he could have won the election."

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Speaking with The New York Times podcast "The Daily," Romney said he expects "unimaginable" consequences for his vote, adding that he does not yet know what they will be.

"My personal and political and team affiliation made me very much not want to convict," he said. "I mean, I want to be with my colleagues in the Senate. I don't want to be the skunk at the garden party. I don't want to have the disdain of Republicans across the country."

Perhaps the strongest criticism was leveled by Trump's eldest son, Donald Trump Jr., which was amplified by his tightknit circle of conservative allies. Trump Jr. tweeted that Romney is "forever bitter he will never be" president, calling him "too weak to beat the Democrats then so he's joining them now."

"He's now officially a member of the resistance & should be expelled from the @GOP," Trump Jr. wrote.

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Romney's own niece Ronna McDaniel, who publicly dropped "Romney" from her name not long after she became chairwoman of the Republican National Committee, tweeted Wednesday that her uncle's vote was not the first time she had disagreed with him and would most likely not be the last. The RNC then sent out an email saying Romney "turns his back on Utah."

Romney's Senate Republican colleagues expressed disappointment but did not excoriate him at the level of Trump and his eldest son. Still, they took him to task.

"I think it's always a dangerous place to be saying that God told you to do something specific," Sen. Tim Scott, R-S.C., said Thursday on "Fox and Friends." "Especially when you have a lot of God-fearing people who are diametrically opposed to your position."

Senate Majority Leader Mitch McConnell, R-Ky., meanwhile, said that while he was "surprised and disappointed," Romney "on the whole has been supportive of what we've been trying to accomplish in the year that he's been there."

Romney's vote to convict Trump on the first article of impeachment, alleging abuse of power, marked the first time in U.S. history that a senator had voted to convict a president of the same party in an impeachment trial. Some of his Republican colleagues, including Susan Collins of Maine, said Trump's conduct regarding Ukraine was wrong, but none were willing to take such a stand.

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Although Romney is not up for re-election until 2024, has had a complicated relationship with the president dating back years, and their previous clashes have caused him headaches with Republicans in Washington and in Utah.

While Romney has at times been highly critical of Trump's conduct, as when he excoriated Trump along the campaign trail in 2016, he had also accepted Trump's endorsement in 2012 and auditioned to be his secretary of state, and he has supported much of Trump's agenda as president.