With the fury over claims in a leaked manuscript of former national security adviser John Bolton’s upcoming book having cooled down somewhat on Capitol Hill, Senate Democrats are signaling likely defeat on their attempt to draw enough defectors to force the Republican-majority Senate to call additional impeachment witnesses, most coveted among them Bolton.

“We’ve always known it will be an uphill fight on witnesses and documents because the president and Mitch McConnell put huge pressure on these folks,” Senate Minority Leader Chuck Schumer (D-NY) said Wednesday.

“Is it more likely than not? Probably no,” Schumer admitted. “But is it a decent, good chance? Yes.”

Schumer’s pessimistic comments, as The New York Times notes, were delivered despite the Democrats devoting most of their questions to attempting to “make the case that an impeachment trial without additional witnesses and documents amounted to a cover-up.”

On the other side of the aisle, optimism prevailed, with Senate Majority Leader McConnell signaling that Republicans would have at least 51 votes to block the Democrats’ demands for witnesses, which Schumer insists the public “overwhelmingly” supports.

The intensified focus on Bolton follows a conveniently timed leak of Bolton’s manuscript, which reportedly claims that Trump told Bolton in August “that he wanted to continue freezing $391 million in security assistance to Ukraine until officials there helped with investigations into Democrats including the Bidens,” as reported by The New York Times on Sunday.

“Mr. Bolton’s explosive account of the matter at the center of Mr. Trump’s impeachment trial, the third in American history, was included in drafts of a manuscript he has circulated in recent weeks to close associates,” the Times reported, citing the accounts of “multiple people” who’d seen the contents of the manuscript. “He also sent a draft to the White House for a standard review process for some current and former administration officials who write books.”

As noted by National Review, after the White House National Security Council warned that Bolton’s book, “The Room Where It Happened: A White House Memoir,” may contain “top secret” information, Bolton’s lawyer disputed the claim on Wednesday, maintaining that Bolton’s team does not believe anything in the book “could reasonably be considered classified.”

Statement of Charles J. Cooper, attorney for @AmbJohnBolton, along with email he sent to NSC asking for relevant chapter of his manuscript dealing with Ukraine to be reviewed ASAP. pic.twitter.com/WCPQmSwHjs — Jake Tapper (@jaketapper) January 29, 2020

Trump has responded to the reports by adamantly denying the claim, tweeting Sunday that he “NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens” and accusing Bolton of just trying to “sell a book.”

“In fact, he never complained about this at the time of his very public termination,” wrote Trump. “If John Bolton said this, it was only to sell a book.”

“With that being said, the transcripts of my calls with President Zelensky are all the proof that is needed, in addition to the fact that President Zelensky & the Foreign Minister of Ukraine said there was no pressure and no problems,” Trump added. “Additionally, I met with President Zelensky at the United Nations (Democrats said I never met) and released the military aid to Ukraine without any conditions or investigations – and far ahead of schedule. I also allowed Ukraine to purchase Javelin anti-tank missiles. My Administration has done far more than the previous Administration.”

Related: ‘GAME OVER’: Trump Posts Video Of Bolton Ukraine Interview, Declares Victory