Within minutes of the Times article, however, Democrats sensed momentum in their push to persuade at least four Senate Republicans to vote in favor of a motion to call witnesses — the minimum they need for such a vote to succeed. That vote is expected in the coming days, during the trial’s second week.

In a joint statement, the seven House impeachment managers said Bolton’s reported account “confirms what we already know” and “directly contradicts the heart” of the defense that Trump’s lawyers have mounted at the trial — that Trump’s decision to suspend the military aid reflected his desire for other countries to chip in.

“There is no defensible reason to wait until his book is published, when the information he has to offer is critical to the most important decision senators must now make — whether to convict the president of impeachable offenses,” the managers added.

Speaker Nancy Pelosi, whose decision to delay the formal transmission of the impeachment articles angered Republicans, said a vote against calling witnesses was “even more indefensible” in light of Bolton’s reported account.

Democrats’ push for witnesses appeared to be sputtering in recent days, with even the small number of Senate Republicans open to calling for new evidence responding skeptically to the House’s case. Democrats contended that the White House’s defense, which began on Saturday, further underscored the need for the Senate to call witnesses; Trump’s team mocked the Democratic case for lacking first-hand witnesses, even though Trump blocked them from testifying.

Democrats have sought testimony from Bolton, Mulvaney and two senior White House budget officials believed to have first-hand knowledge of Trump’s decision to withhold military aid from Ukraine. Other witnesses testified that they came to believe that Trump withheld the aid and a White House meeting with President Volodymyr Zelensky of Ukraine in order to pressure the country to launch politically motivated investigations, but those witnesses pointed to others — like Bolton and Mulvaney — who would know better than they would.

Charles Cooper, Bolton’s attorney, said in a statement that the White House’s review process of the manuscript had been “corrupted.” A printed manuscript of the book was delivered to the National Security Council’s Records Management Division on December 30 to review for classified information.

“We submitted the manuscript notwithstanding our firm belief that the manuscript contained no information that could reasonably be considered classified and on the assurance that the "process of reviewing submitted materials is restricted to those career government officials and employees regularly charged with responsibility for such reviews" and that the “contents of Ambassador Bolton’s manuscript will not be reviewed or otherwise disclosed to any persons not regularly involved in that process," Cooper said in a statement.

“It is clear, regrettably, from The New York Times article published today that the prepublication review process has been corrupted and that information has been disclosed by persons other than those properly involved in reviewing the manuscript,” Cooper added.

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