Americans and the men and women who represent them in the U.S. Senate need to hear sworn testimony from former national security adviser John Bolton.

The Republican effort to block witness testimony and critical evidence from being presented in the impeachment trial of President Donald Trump is indefensible, even more so now that the nation has learned that the manuscript of an upcoming book written by Bolton and leaked to the New York Times directly contradicts the narrative presented by the president's defenders.

The manuscript was sent to the White House for a standard national-security review on Dec. 30. Since then, the White House has been aware of its explosive contents, including that Trump told Bolton the freeze on $391 million in security assistance for a U.S. ally defending itself against Russian aggression would remain in place unless or until Ukrainian officials launched a public investigation into a domestic political rival.

Bolton also alleges that other key administration figures were dishonest in their dealings. Secretary of State Mike Pompeo, Bolton wrote, privately admitted that then-ambassador to Ukraine Marie Yovanovitch was not corrupt, contradicting Trump's personal attorney; that Attorney General William Barr knew about the president's phone call with Ukrainian President Volodymyr Zelensky earlier than he has indicated; and that acting Chief of Staff Mick Mulvaney was present for one of Trump's phone calls about Yovanovitch with the president's personal attorney, Rudolph Giuliani, despite Mulvaney's claims otherwise.

Trump has disputed Bolton's claims in a series of (what else?) tweets, some of which contain falsehoods, including that the House had not sought to interview Bolton. It did, Bolton said no, and the House — fearing a long legal fight — did not subpoena him. Trump also tweeted that "if John Bolton said this, it was only to sell a book," a pathetic defense that some senators seemed to coalesce around on Monday as they reeled from the revelations.

Let's remember that the Senate, as is its constitutional duty, is conducting a trial. What kind of jurors, in any venue, wouldn't want, indeed demand, relevant testimony and evidence in order to fairly adjudicate a case? In the Trump trial, those senators committed to protecting and defending the president at all costs aren't interested in the truth.

The Bolton book is just the latest example. The Senate should also be reviewing the recently released recording from Giuliani associate Lev Parnas (whom Trump falsely claimed he did not know) that shows the president saying of Yovanovitch, "Get rid of her."

The title of Bolton's book, "The Room Where it Happened," is also the name of a song in the musical "Hamilton" that references insider access affecting political decisions.

Bolton was in the room where it happened. Senators, and the country, should hear from him, under oath. Only the truth will honor and uphold the constitutional principles that Alexander Hamilton and his fellow Founding Fathers gifted to the nation.