Democrat impeachment managers pushing to oust Donald Trump as president in the ongoing Senate impeachment trial are now demanding Republicans call former national security adviser John Bolton to testify. This demand comes after a bombshell exposé Sunday Trump ordered the U.S. government to continue withholding military aid to Ukraine until the country helped with investigations into Joe Biden he demanded.

The New York Times made the revelation, which some political pundits claim has the potential to change course of impeachment trial, in a story based on an unpublished draft manuscript of Bolton's upcoming book it had obtained. The book, "The Room Where It Happened; A White House Memoir," will be released March 17.

The most damning parts of Bolton's draft are passages saying Trump told Bolton during a conversation they had in August 2018 to withhold congressionally-approved military aid for Ukraine until Ukrainian officials led by president Volodymyr Zelensky helped with the Biden investigation Trump kept demanding.

Bolton's book directly tied the release of U.S. military aid amounting to $390 million to Ukraine investigating Biden and his son, Hunter to help Trump's reelection campaign. Bolton's explosive revelation directly gives lie to a central theme of Trump's defense repeated ad nauseam there was no quid pro quo between Trump and Zelensky.

Bolton also directly implicated other Trump underlings such as acting White House chief-of-staff Mick Mulvaney and state department secretary Mike Pompeo in the Ukraine scandal.

The seven House Democrat impeachment managers said the exposé confirms, "What we already know."

"There can be no doubt now that Mr. Bolton directly contradicts the heart of the President's defense and therefore must be called as a witness at the impeachment trial of President Trump," said the managers in a joint statement Sunday evening reacting to the Times' report.

"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 House managers said Americans know a fair trial must include both the documents and witnesses blocked by Trump and "that starts with Mr. Bolton." Other congressional Democrats also demand Bolton testify at the Senate trial.

"Amb. Bolton reportedly heard directly from Trump that aid for Ukraine was tied to political investigations," tweeted House majority leader Nancy Pelosi, D-CA. "The refusal of the Senate to call for him, other relevant witnesses, and documents is now even more indefensible. The choice is clear: our Constitution, or a cover-up."

Senate minority leader Chuck Schumer, D-NY, echoed Pelosi's sentiments, tweeting, "It's up to four Senate Republicans to ensure that John Bolton, Mick Mulvaney, and the others with direct knowledge of President Trump's actions testify in the Senate trial."

In the draft book manuscript, Bolton describes how the Ukraine scandal developed in his final months in the White House, including new details about different senior administration officials' involvement, according to the Times.

As might be expected, Trump strongly denied Bolton's assertions. He tweeted: ""I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens. In fact, he never complained about this at the time of his very public termination. If John Bolton said this, it was only to sell a book."