The jolting revelations from John Bolton’s manuscript revived talk on Capitol Hill of a witness swap as a way to hear from the former national security adviser in President Trump’s impeachment trial.

Sen. Patrick Toomey, R-Pa., reportedly became the latest GOP senator to support witnesses. He pitched the idea of a “one-for-one” swap during a closed-door lunch with GOP senators on Monday – one witness for House managers and one for Trump's defense team, the Washington Post reported.

Meanwhile, Sen. Mitt Romney, R-Utah, who has long said he wants to hear from Bolton, “made a strong pitch” for witnesses during the GOP lunch Monday, according to Politico. To convince his fellow Republicans to hear from Bolton, Romney acknowledges it may require a deal on bringing on witnesses that Trump wants. Hunter Biden is among the potential witnesses Trump allies have sought.

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“My expectation is that were there to be that testimony from Mr. Bolton, that there would be testimony from someone on the defense side as well in order to get some 50-plus people to agree,” Romney said. “I’m not going to be counting noses as to who would support or not support that at this stage, but I may down the road.”

It would take four GOP defectors to join with all Democrats to get the 51 votes necessary to force new witnesses to the trial. Romney and Sen. Susan Collins, R-Maine, have long spoken favorably of witnesses once the first phase of the trial is completed – likely by Friday.

Sens. Lisa Murkowski, R-Alaska, and Lamar Alexander, R-Tenn., have also expressed an openness to considering witnesses, while Majority Leader Mitch McConnell has pressed for a swift trial and vote to acquit.

The urgency to get Bolton to the Senate trial comes after the New York Times reported that Bolton's manuscript included a claim that Trump explicitly linked a hold on Ukraine aid to an investigation of Joe and Hunter Biden. Trump told Bolton in August, according to a transcript of Bolton's forthcoming book reviewed by the Times, "that he wanted to continue freezing $391 million in security assistance to Ukraine until officials there helped with investigations into Democrats including the Bidens."

Some Republicans, for their part, have called for both Bidens and the unnamed whistleblower to show up at trial, too, if the Senate votes for witnesses. Leading Democrats, however, have quashed talk of a potential swap saying the Bidens are not relevant witnesses to the two underlying articles of impeachment -- abuse of power and obstruction of Congress. A senior Democratic official working on the impeachment trial said Tuesday they won't subject the Bidens to an "irrelevant smear campaign."

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But Sen. Ted Cruz, R-Texas, has said Hunter Biden’s testimony is “relevant” and Sen. Josh Hawley, R-Mo., said Biden’s son is a “material witness."

One potential off-ramp is getting ahold of Bolton's manuscript without actually calling the man himself to testify before the Senate. Sen. Lindsey Graham, R-S.C., said he'll seek to get a copy of the unpublished book. Sen. James Lankford, R-Okla., said in a Facebook video that senators should be given access to the manuscript.

“I think getting that information first-hand would be really important for us,” said Lankford, who also urged Bolton to speak out publicly. "...There’s plenty of microphones all over the country that he should step forward and start talking about it right now.”

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But Romney is stuck on seeing Bolton testify. Asked if he'd be satisfied with just the manuscript, the former GOP presidential nominee said, “I’d like to hear from Mr. Bolton.”

Democratic Leader Chuck Schumer Tuesday called the idea of viewing Bolton’s manuscript in a classified SCIF “absurd” and said there’s no substitute for questioning a witness under oath. Schumer ruled out a witness swap for Hunter Biden.

“Hunter Biden has nothing to do with the facts of this trial,” Schumer, D-N.Y., said.

Democrats view Bolton’s testimony as instrumental in making their case that Trump abused his power for personal gain and providing the necessary first-hand knowledge of a quid pro quo. Bolton declined to show up for the House impeachment inquiry but said he’d comply with a Senate subpoena.

Trump has denied Bolton’s allegations and accused Bolton of just trying to peddle a book. His lawyers argued if Bolton’s allegations are true, it’s still not impeachable conduct because there is no underlying crime.

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Democrats say the first step to any fair trial is witnesses, and Bolton is on top of the list.

“If the senators don't find that there aren't enough direct witnesses of the president's misconduct, there's one volunteering, almost begging to come in,” Rep. Adam Schiff, D-Calif., told MSNBC Tuesday. “And instead, many of them want to bury their head in the sand."

Fox News' Jason Donner contributed to this report.