An explosive Sunday night leak on ex-Trump adviser John Bolton’s forthcoming memoir—which reportedly reveals a first-hand account of the president’s desire to withhold aid to Ukraine in exchange for investigations of his political rivals—left Senate Republicans scrambling on Monday to keep their plans for a speedy acquittal of the president.

By midday, GOP lawmakers had already thrown out all manner of excuses to justify rejecting a vote to call additional witnesses (of which Bolton would be one) and evidence in Trump’s impeachment trial. The Bolton disclosure, which was reported by The New York Times, reportedly took them by surprise and forced Republicans to dig even deeper as swing votes like Sens. Mitt Romney (UT) and Susan Collins (ME) declared that they were even closer to supporting additional witness testimony.

“I think it’s increasingly clear, what John Bolton would have to say would be important for those of us who are asked to render impartial justice,” Romney told reporters, adding that he had not yet spoken with other members and couldn’t guess how the news had impacted them.

Beyond Romney and Collins, however, Democrats would still need two more Republicans to join them in voting for witnesses—a vote that is not expected to occur until later this week. And it was unclear on Monday afternoon whether the Bolton news would compel those GOP defectors to come forward.

One member, Sen. Lamar Alexander (R-TN), who has not said whether he’ll vote for witnesses, remained tight-lipped Monday, saying he would make that determination “after we’ve heard all the arguments, after we’ve heard the questions and the answers to the questions... then we’ll have that vote.”

Asked by a reporter if he thought Bolton had shifted the dynamic at all, Alexander replied, “I can’t say anything more than I’ve just said.”

That more Senate Republicans weren’t publicly jarred by news of Bolton’s manuscript illustrated the degree to which the party has remained committed to keeping President Donald Trump’s impeachment trial as tight and succinct as possible. Indeed, in the immediate aftermath, the party’s main actors and committees chose to fire back at Bolton by portraying him as opportunistic and aggrieved. Even the Republican National Committee put out a press release attacking Bolton, who has raised and spent thousands to elect GOP lawmakers through his super PAC.

The Bolton news came as the president’s defense team was set to spend a full day on the Senate floor laying out their case to acquit Trump. Many GOP senators urged reporters to “take a breath” and let the White House make its case before coming to any judgments.

Republicans who had already been inclined to side with the president, meanwhile, threw out new reasons to not put Bolton or other witnesses under oath. Sen. Roy Blunt (R-MO) blamed House Democrats for not securing Bolton’s testimony and warned that calling witnesses would pose thorny legal questions that would prolong the trial.

“It’s the House’s job to put a case together,” said Blunt. “It’s then our job to deal with that in a prompt manner. Unless there’s a witness that’s going to change the outcome, I can’t imagine why we'd want to stretch this out for weeks and months. And if we call any witnesses that are subject to privilege, it would take weeks at least.”

When asked, other Republicans didn’t engage with the substance of the report but instead raised the notion that the timing of the leak was suspicious.

“The timing on this was not a coincidence,” said Sen. Steve Daines (R-MT) as he dashed into a Republican members’ lunch.

Speaking to reporters at a press conference, Sen. Mike Braun (R-IN) didn’t deny that the news had changed the dynamic of a trial that just 24 hours ago was seemingly speeding to a quick resolution in favor of an acquittal.

“I think it is clear the question of witnesses was going to come up anyway and in this case, it may move the needle in one direction or another,” said Braun. “I’m not going to deny it’s going to change the decibel level and probably the intensity with which we go about talking about witnesses.”

Democrats hammered the news as yet another reason why additional witnesses and evidence must be subpoenaed. Rep. Adam Schiff (D-CA), the lead impeachment manager, told reporters that Senate Republicans “appear to be reconsidering.”

“He ought to come in, testify under oath… senators should not wait until Mar. 17 when the book comes out,” Schiff said. “It’s not a question of whether I trust John Bolton or the Republican senators trust him. He should be placed under oath.”