Washington CNN  — 

Republican Sen. Mitt Romney harshly criticized President Donald Trump on Wednesday over his actions toward Ukraine, saying the President is “guilty of an appalling abuse of public trust” in an emotional speech on the Senate floor.

In a stunning break with his own party, the Utah Republican voted to convict the President on the abuse of power charge brought by the House in the impeachment trial, making him the only Republican senator to vote to convict on one of the two articles of impeachment. He voted to acquit on the second article, 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,” Romney said. “Yes, he did.”

“The President asked a foreign government to investigate his political rival. The President withheld vital military funds from that government to press it to do so. The President delayed funds for an American ally at war with Russian invaders,” he continued.

“The President’s purpose was personal and political. Accordingly, the President is guilty of an appalling abuse of public trust,” Romney said.

Romney, an occasional critic of the President, had been closely watched as a potential swing vote. His decision immediately opened him up to criticism from within his own party and the President, who has urged party unity during impeachment proceedings.

During his floor speech, Romney spoke of his own faith and of the possibility for retribution he may face over his decision during the speech.

“I’m aware that there are people in my party and in my own state who will strenuously disapprove of my decision and in some quarters I will be vehemently denounced. I’m sure to hear abuse from the President and his supporters,” he said, “Does anyone seriously believe that I would consent to these consequences other than from an inescapable conviction that my oath before God demanded it of me?”

Romney said at one point, “My faith is at the heart of who I am,” pausing to collect himself before he began speaking again.

“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. I was not wrong,” he said.

House Republicans were united in rejecting the impeachment articles in the House and the GOP-led Senate voted to acquit Trump on Wednesday.

Romney had been careful not to show his hand during the trial on how he ultimately planned to vote. He did, however, cross party lines last week to vote in favor of the unsuccessful attempt to allow additional witnesses to testify.

This story has been updated to reflect Wednesday’s votes to acquit Trump.