Faced with an unwelcome offer from former National Security Adviser John Bolton to testify in an impeachment trial if subpoenaed, Senate Republicans responded with righteous anger toward Democrats, dry deference to the facts of the impeachment process—and, in the case of Sen. Ted Cruz (R-TX), a request to call his office on the matter.

Few GOP lawmakers, however, responded with a simple answer as to whether a figure at the heart of the impeachment case against President Trump should offer his account of events under oath.

In fact, just one—Sen. Mitt Romney (R-UT)—said outright that the jurors in the impeachment trial should hear from Bolton. “He has firsthand information,” Romney told reporters on Monday. “And, assuming that articles of impeachment reach the Senate, I'd like to hear what he has to say.”

Bolton’s surprise announcement came at an inopportune moment for the Senate GOP, which seemed poised to head into an impeachment trial this month under the terms preferred by Trump and his allies—namely, a short proceeding featuring no new witnesses. Since the House’s vote to impeach on Dec. 19, Speaker Nancy Pelosi has sat on the articles of impeachment, saying she’d send them to the Senate when and if the ground rules of the trial seemed fair, in a bid to put pressure on Senate Majority Leader Mitch McConnell (R-KY).

Bolton, who left the White House on less than cordial terms in September, is one of just a few essential missing links in the story of Trump’s apparent campaign to withhold U.S. security aid to Ukraine in hopes of getting that government to investigate his political rivals. According to Bolton’s aides, who testified to House impeachment investigators, the national security chief bristled at the push, going so far as to call it a “drug deal” he wanted no part of.

Whatever misgivings Bolton may have had about Trump’s conduct, his reluctance so far to testify—and his coyness on the subject, complete with teases to his forthcoming tell-all book—has been a source of deep frustration on Capitol Hill. He declined to testify during the House’s impeachment inquiry, pointing to an ongoing court case meant to resolve whether or not a former aide, Charles Kupperman, could defy a presidential directive to not cooperate with Congress, even if under subpoena. House Democrats ultimately never issued a subpoena for Bolton’s testimony.

On Monday, Bolton declared in a post on his political action committee’s website that it “does not appear possible that a final judicial resolution” of the constitutional question at hand will be rendered before the Senate trial, so he said he would cooperate with a subpoena if issued by the Senate.

Until Bolton’s announcement, there was a growing sense on Capitol Hill that Pelosi would have to relinquish the articles—and control of the process to McConnell—this week. Bolton’s move changed that calculus, and while GOP senators evinced some frustration with him, most of the anger was directed at Pelosi.

“One of the dangers of Speaker Pelosi sitting on these articles indefinitely,” said Sen. Josh Hawley (R-MO), “is, I think we will see—unless someone does something—an endless attempt to keep adding stuff to the articles. ‘Oh well what about this, oh well what about that, but what about this’… the American people deserve a resolution here.”

And Sen. John Barasso (R-WY), the No. 3 member of the Senate GOP leadership, said the call for Bolton’s testimony showed how “desperate” the Democrats were and “how poorly a job they did in the House of establishing a credible case.”

Democrats may have held off on a subpoena for Bolton but undoubtedly wanted to secure his testimony. And some Senate Republicans said they’d be fine with Bolton testifying—if it were on the House side.

“I don't have any opposition if the ambassador's willing to testify and the House is willing to convene and do that, then they're more than welcome to do that,” said Sen. Thom Tillis (R-NC). “What I don't want to do is all of a sudden open it up to where we effectively have the impeachment inquiry on the Senate side… I’m encouraging the House to do the job they should have done to begin with.”

But Democrats from both sides of the Capitol sought to put the pressure squarely on Republicans—four of whom would need to join all Democrats in a vote to approve a subpoena for Bolton—rather than entertain the idea that the House simply do it.

House Intelligence Committee Chairman Adam Schiff (D-CA), who led the impeachment inquiry, told reporters on Monday that he wouldn’t foreclose the possibility he would subpoena Bolton but made clear it was the Senate’s responsibility first. “He really should testify in the Senate trial,” said Schiff.

Aside from Romney, however, several of the senators who could conceivably vote with Democrats to approve a Bolton subpoena deferred to process, attempting to punt a discussion on the merits of hearing Bolton’s account of the Ukraine story until the trial formally begins.

Sen. Susan Collins (R-ME) said she wanted to see the Senate proceed as it did during the impeachment of Bill Clinton, during which senators first voted to open a trial and later voted on calling of additional witnesses. Pressed as to whether she wanted to see Bolton testify, Collins told reporters the decision would be made later. Another like-minded lawmaker, Sen. Lisa Murkowski (R-AL), echoed Collins’ remarks.

"I think we need to do what they did the last time they did this,” Murkowski told reporters Monday night, “and that was to go through a first phase, and then they reassessed after that,"

Still other Republicans already seemed exasperated by Bolton’s maneuvers. Sen. Ron Johnson (R-WI), who has traveled to Ukraine and spoke to key players in the saga at various points, said it was possible Bolton might have exculpatory information on Trump’s conduct but declared that Democrats and the media would blow it out of proportion if he did ultimately testify.

“Having been involved, having spoken with John Bolton myself on this issue, I don't know what additional information he might have,” said Johnson. “I don't think it'd be particularly revealing.”