Sen. Mitt Romney (R-Utah) will vote to convict President Trump for abuse of power and acquit him for obstruction of Congress in the Senate impeachment trial.

Why it matters: Romney is the only Republican senator to break ranks and vote to remove Trump from office, though the president is still expected to be acquitted later today.

Romney — who appeared choked up on the Senate floor as he announced his vote — was the Democrats' last chance for a bipartisan conviction vote, after Sen. Susan Collins (R-Maine) announced Tuesday that she will vote to acquit the president.

Romney and Collins were the only two Republican senators who voted last week to allow witnesses and documents in the trial — a call that otherwise failed along party lines.

Between the lines: The decision is sure to infuriate Trump, who has railed against Romney several times in the past over the senator's criticisms of his conduct.

Even if Democratic Sens. Joe Manchin (D-W.Va.) and Kyrsten Sinema (D-Ariz.) vote to acquit Trump, the president will not be able to tout a bipartisan acquittal without the context that there was a bipartisan call to remove him from office.

Romney will become the first senator ever to vote to remove a president who belongs to their own party.

What he's saying:

"The president delayed funds for an American ally at war with Russian invaders," Romney said in a speech on the Senate floor. "The president's purpose was personal and political. Accordingly, the president is guilty of an appalling abuse of public trust."

"What he did was not perfect," he continued. "No, it was a flagrant assault on our electoral rights, our national security and our fundamental values. 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."

Romney also acknowledged the potential political backlash from his decision, stating, "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?"

This story is breaking news. Please check back for updates.

Editor's note: This story has been corrected to reflect that Sen. Susan Collins represents Maine (not Utah).