Washington CNN  — 

Sen. Mitt Romney’s vote on Wednesday to convict President Donald Trump on one of the articles of impeachment not only rankled his fellow Republicans but also led his niece, the chairwoman of the Republican National Committee, to publicly disagree with him.

Romney’s decision came as a surprise to his Republican Senate colleagues and was swiftly met with condemnation from the President and many of his allies.

“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 wrote in an overnight tweet, referring to Romney’s 2012 bid. “Read the Transcripts!”

RNC Chairwoman Ronna McDaniel distanced herself from her uncle, as she has previously done when Romney has criticized Trump.

“This is not the first time I have disagreed with Mitt, and I imagine it will not be the last,” McDaniel tweeted. “The bottom line is President Trump did nothing wrong, and the Republican Party is more united than ever behind him. I, along with the @GOP, stand with President Trump.”

The Utah Republican Party tweeted its own criticism of the junior senator from the Beehive State later on Wednesday.

“The Utah Republican Party is pleased to see President Trump completely acquitted by the United States Senate,” the party said in a post from its account. “We appreciate the service rendered to our state by Utah’s two senators. As a party, we strongly disagree with the vote cast today by Senator Romney.

“We stand firmly behind our President, whose policies have created unprecedented levels of American prosperity. The impeachment effort has served only to distract America from the serious issues we face, and in November voters will hold Democrats accountable for this distraction.”

Vice President Mike Pence called Romney’s decision a “disappointment” during an interview on radio’s “The Lars Larson Show” but added that “at the end of the day it makes no difference.”

Donald Trump Jr. mocked Romney over his decision in a series of tweets, calling him “bitter” and saying he should be expelled from the Senate Republican conference. Matt Schlapp, chairman of the Conservative Political Action Conference, who said last month that Romney would not be invited to the conservative conference because of his support of witness testimony, also mocked Romney on Twitter Wednesday.

Frustration among Senate colleagues

Romney did not tell any colleagues about his decision in advance of his announcement Wednesday. Although some Republicans have publicly said the Utah senator’s vote was a personal choice and one they generally respect, behind the scenes there was significant frustration with his decision.

“I’ll give him this: professional rollout,” one GOP senator told CNN. “Not very collegial, but very professional.”

A bigger issue, several GOP aides said, was the possibility Romney’s decision would step on the headline of the President’s acquittal in the media.

“All you guys are going to lead with Romney,” one senior GOP aide said. “Not the fact the President was acquitted and is through with this.”

When reporters asked Mississippi GOP Sen. Roger Wicker just minutes after the vote to react, Wicker replied: “This is his hour.”

Another GOP aide guessed that Romney wasn’t having “much fun” right now.

Mike Lee, Utah’s other Republican senator, didn’t name Romney in a tweet Wednesday evening but seemed to send a clear message.

“Congratulations @realDonaldTrump. I’m looking forward to your next five years in office. Those who voted to remove you were wrong. Very wrong,” Lee said.

Before the vote, members of GOP leadership had projected confidence that Romney would vote with them, only to be surprised watching his announcement on TV.

Romney had stood apart from his Republican colleagues in the past week, as his pleas in closed-door meetings for witnesses and documents were largely scoffed at and ignored, according to people in the room.

Romney announced in a Senate floor speech Wednesday afternoon that he would vote to convict the President on an abuse of power charge levied by House Democrats. He voted not guilty on the second article of impeachment, obstruction of Congress.

“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,” the Utah Republican said on the Senate floor. “Corrupting an election to keep oneself in office is perhaps the most abusive and destructive violation of one’s oath of office that I can imagine.”

Sen. John Thune, a South Dakota Republican, told reporters ahead of Wednesday’s vote that he thought senators would accept Romney’s decision and continue to work with him despite his vote.

“You know, in the conference, he’s somebody who we all know is a very independent person and, obviously, you know, we’re going to continue to work with him,” said Thune, the second-ranking senator in GOP leadership. “There is always another day and another vote, and you may not have everybody on every vote. Sometimes you just have to play the next game when it comes along. So we’ll be prepared for whatever comes next. And so will he, and I’m sure that the members of our conference will continue to work with him and accept his point of view.”

CNN’s Nikki Carvajal and Ted Barrett contributed to this report.