Washington • Sen. Mitt Romney said Monday he would like to hear from former national security adviser John Bolton about the forthcoming impeachment trial of President Donald Trump, signaling a possible key vote to allow witnesses despite resistance by GOP leaders.

Romney, who previously has said he’d speak out about his thoughts on witnesses at a later date, told reporters Monday that Bolton could be a crucial voice as the Senate considers charges of abuse of power and obstruction of Congress against Trump.

Asked whether that would include Bolton — who earlier Monday said he would testify if asked — Romney said “of course” he’d like to hear from him.

“He has firsthand information and assuming that articles of impeachment reach the Senate, I’d like to hear what he has to say,” Romney said.

The Democrat-led House has yet to send over the two articles of impeachment while urging Senate Majority Leader Mitch McConnell to hold an actual trial rather than rush through a vote in the GOP-controlled chamber that is expected to acquit Trump.

Bolton, who was in the White House when the president withheld hundreds of millions of dollars in congressionally mandated aid to Ukraine while asking its new president to announce investigations into a political rival, said Monday he had been waiting on a judicial ruling in a related case on whether he should testify but that case became moot after the House passed impeachment articles.

Democrats have argued that Bolton, as well as acting White House chief of staff Mick Mulvaney, should be called before the Senate to offer their recollections of how the Ukraine situation unfolded and Bolton said he’d be willing if subpoenaed.

“Accordingly, since my testimony is once again at issue, I have had to resolve the serious competing issues as best I could, based on careful consideration and study,” he said in a statement. “I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify.

Republicans hold 53 seats in the Senate but a few defections from its ranks could change the rules in how the impeachment trial proceeds.

It takes a simple majority vote to set the trial rules.

Collins said recently that she was shocked that senators were already lining up on either side of Trump before the trial even began.

“There are senators on both sides of the aisle who, to me, are not giving the appearance of — and the reality of — judging this in an impartial way," she told Maine Public Radio last week.

Romney, who has clashed with Trump before and after taking office, has repeatedly said that he isn't staking out a position on the impeachment trial.

I am going to remain unbiased and a true juror,” he told The Salt Lake Tribune recently.

While Romney may be the first GOP senator to suggest hearing from Bolton, fellow Republicans so far disagree.

“The testimony & evidence considered in a Senate impeachment trial should be the same testimony & evidence the House relied upon when they passed the Articles of Impeachment,” Sen. Marco Rubio, R-Fla., tweeted Monday. “Our job is to vote on what the House passed, not to conduct an open ended inquiry.”

Trump phoned into conservative radio host Rush Limbaugh’s show on Monday afternoon to vent about the impeachment process, adding to comments on Twitter earlier that it is taking away from his more important work as president, including dealing with an escalating standoff in the Middle East.

“It’s so sad for our country. I mean think of it," Trump told the radio host. “Our country is doing so good. But I have to spend, and my team has to spend time on this stuff. They found nothing.”

White House senior adviser KellyAnne Conway lamented that House Speaker Nancy Pelosi has yet to physically send over the impeachment articles for the Senate to start its trial.

“Which is it?” Conway said. “Is the president an imminent threat to the republic, a clear and present danger who must be removed immediately? Or did [Pelosi] take a little mini-sabbatical over the break?”

Conway added that Trump doesn't want a delay — he wants to be acquitted.

“He knows the trial is going nowhere,” she said. “He wants a full and fair trial, but that doesn’t mean a lengthy one. Those articles of impeachment are very thin.”