The vote failed, all but guaranteeing Trump's acquittal next week.

While CPAC has grown into a hotbed of Trumpian support, Romney has distanced himself from the president, garnering Trump's mockery and scorn.

Trump's antipathy toward Romney long predates his impeachment, and the president has run supercuts of Romney's defeat in the 2012 presidential election to mock the senator.

Romney called for more information as reports first circulated of Trump pushing Ukraine to investigate his political rivals.

"If the President asked or pressured Ukraine’s president to investigate his political rival, either directly or through his personal attorney, it would be troubling in the extreme. Critical for the facts to come out," Romney tweeted in September.

Trump was charged with abuse of power and obstruction of Congress after pushing Ukrainian officials to publicly launch a corruption investigation into the son of Democratic presidential candidate and former Vice President Joe Biden.

Mike Lee, Utah's Republican senior senator and a frequent CPAC attendee, tweeted a message of support shortly after Schlapp's announcement.

"Mitt Romney is a good friend and an excellent Senator. We have disagreed about a lot in this trial. But he has my respect for the thoughtfulness, integrity, and guts he has shown throughout this process," Lee wrote. "Utah and the Senate are lucky to have him."

Romney has previously spoken at the annual conservative conference including his first public speech since losing the 2012 election. He also spoke at CPAC in 2012 calling himself a "severely conservative governor" in an effort to shore up more support from the party's right as he sought the nomination.