Romney: 'Increasingly likely' other Republicans will join his call for witnesses

"I've said for some time that I would hope to hear from John Bolton. I think with the story that came out yesterday that it is increasingly apparent that it would be important to hear from John Bolton," the Utah Republican said. "I think it's increasingly likely that other Republicans will join those of us who think we should hear from John Bolton."

LIVE UPDATES: Impeachment trial of President Trump

Romney, who has before expressed frustration with Trump, previously indicated that he would be interested in hearing testimony from Bolton. "I think it's very likely I'll be in favor of witnesses, but I haven't made a decision finally yet and I won't until the testimony is completed," he said.

"I am not going to speak for any other Republican senators," Romney said when asked Monday who he has spoken with. "I have spoken with others who have opined on this as well."

The President's legal team resumed its second day of arguments on Monday, but all of the attention will be focused on the Republican senators sitting in the chamber and how they react to Sunday night's New York Times bombshell that Bolton's draft manuscript says Trump told him US security assistance to Ukraine was conditioned on investigations into Democrats, including former Vice President Joe Biden. Trump's attempts to pressure Ukraine to investigate Hunter Biden and Joe Biden, his potential political rival, are at the center of the President's impeachment trial.

Trump has repeatedly made unfounded and false claims to allege that the Bidens acted improperly in Ukraine. There is no evidence of wrongdoing by either Joe or Hunter Biden.

Democrats need four Republicans to vote with them in favor of subpoenas for witnesses or new evidence in order to extend the trial and gather new information. Four senators, specifically, are being closely watched to vote for those subpoenas. That short list includes Romney, moderate Sens. Susan Collins of Maine and Lisa Murkowski of Alaska, and endangered senators up for reelection like Sen. Cory Gardner of Colorado.

Collins said Monday morning that "the reporting on John Bolton strengthens the case for witnesses and has prompted a number of conversations among my colleagues."

"I think fairness requires us to allow both sides to present their cases before we move to the issue of witnesses, and I've worked very hard to get language in the governing resolution that would ensure a vote on whether or not to call witnesses and subpoena other documents," she told a small group of reporters in the Capitol. "I've also said from the beginning that it was very likely that I would vote for witnesses. And that has not changed."

Murkowski released her own statement Monday, saying "I stated before that I was curious as to what John Bolton might have to say.

"From the outset, I've worked to ensure this trial would be fair and that members would have the opportunity to weigh in after its initial phase to determine if we need more information," Murkowski said. "I've also said there is an appropriate time for us to evaluate whether we need additional information —that time is almost here. I look forward to the White House wrapping up presentation of its case."