In his upcoming memoir, The New York Times reports, former National Security Adviser John Bolton says Donald Trump explicitly drew a connection between his delay of congressionally approved military aid to Ukraine and "investigations into Democrats," including former Vice President Joe Biden and his son Hunter. That account, which is based on interviews with "multiple people" who have seen Bolton's manuscript, helps explain why the White House, where copies of the book have circulated as part of the prepublication review process, is keen to prevent Bolton from testifying during Trump's impeachment trial.

The Times notes that Bolton's description of Trump's motive "could undercut a key element of his impeachment defense: that the holdup in aid was separate from Mr. Trump's requests that Ukraine announce investigations into his perceived enemies." But there has always been a tension between that "key element" and another argument deployed by Trump's lawyers, who say his request for what he has described as "a major investigation into the Bidens" was perfectly legitimate, reflecting his sincere concern about rooting out official corruption in Ukraine.

In the memoir, the Times says, Bolton describes how he, Secretary of State Mike Pompeo, and Defense Secretary Mark Esper unsuccessfully urged Trump to release the aid "nearly a dozen times." During an August 2019 discussion of the issue, Trump said "he preferred sending no assistance to Ukraine until officials had turned over all materials they had about the Russia investigation that related to Mr. Biden and supporters of Mrs. Clinton in Ukraine."

That description makes it sound like Trump's focus in his conversation with Bolton was not on the dubious allegation he raised during his July 25 telephone call with Ukrainian President Volodomyr Zelenskiy—i.e., that Biden had improperly used his influence as vice president to help his son by pressuring the Ukrainian government into firing a prosecutor who was investigating Burisma, an energy company that employed Hunter Biden as a board member. Instead it sounds like Trump was complaining about Ukraine's supposed role in instigating the investigation of Russia's attempts to influence the 2016 presidential election, including possible collusion between Russian agents and the Trump campaign. It's not clear exactly how Biden figures into that purported plot to undermine Trump.

Trump nevertheless thought it was important to deny that he said what Bolton reportedly claims he said. "I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens," the president wrote on Twitter last night. "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."

Trump added that he "released the military aid to Ukraine without any conditions or investigations—and far ahead of schedule." That last part, of course, is plainly not true, since Ukrainian officials, Trump's own appointees (evidently including not only Bolton but also Pompeo and Esper), and members of Congress from both parties were all concerned about the Trump-ordered delay of the military assistance. Trump released the aid only after the delay became public and controversial, partly because of a whistleblower's complaint that Trump was improperly pressuring Ukraine into announcing an investigation of Biden with the aim of discrediting a political rival and improving his re-election prospects.

Trump's defense also ignores the fact that Zelenskiy had scheduled a CNN interview during which he planned to announce the investigations that Trump wanted of the Bidens and of alleged Ukrainian efforts to help Hillary Clinton win the 2016 election. Zelenskiy canceled that interview only after Trump released the aid and after William Taylor, the acting U.S. ambassador to Ukraine, urged him to do so.

Trump's lawyers have said he delayed the aid partly because he was concerned about Ukrainian corruption. They also have said the investigations he sought reflected that concern. In other words, they have implicitly conceded that there was a connection between the aid and those investigations, which supposedly would have been a sign that Zelenskiy was serious about tackling corruption.

At an October 17 press briefing, acting White House Chief of Staff Mick Mulvaney said "the corruption related to the DNC server"—i.e., the fantastical notion that the server from which Democratic National Committee emails were stolen in 2016 was stashed away somewhere in Ukraine—"absolutely" did figure into the aid delay. "No question about that," he said. "But that's it. And that's why we held up the money."

Today a lawyer for Mulvaney directly contradicted his client's October 17 statement, saying Mulvaney never had "a conversation with the President or anyone else indicating that Ukrainian military aid was withheld in exchange for a Ukrainian investigation of Burisma, the Bidens, or the 2016 election." When Mulvaney referred to "the corruption related to the DNC server," he was clearly talking about the 2016 election—specifically, a bizarre conspiracy theory alleging that Ukrainians stole the DNC emails and framed Russia for that crime in an attempt to discredit Trump and help Clinton.

Back in October, Mulvaney did say "the money held up had absolutely nothing to do with Biden." But if investigating Biden was perfectly appropriate, as the president and his lawyers insist, why deny that connection? Presumably because using the aid to pressure Ukraine into announcing an investigation of the leading contender to oppose Trump in this year's election—the quid pro quo at the heart of Trump's impeachment—looks an awful lot like an abuse of power for personal gain. If Trump specifically mentioned Biden while defending the aid freeze to Bolton, especially if he mentioned Biden in connection with the Russia investigation rather than Burisma, it reinforces the impression that Trump's aim was tarnishing a political opponent's reputation.

Bolton, who declined to testify during the House impeachment hearings because Trump did not want him to do so, has said he is prepared to testify in Trump's Senate trial if he receives a subpoena. The votes of four Republicans would be required to approve such a subpoena. Today two Republican senators, Susan Collins of Maine and Mitt Romney of Utah, said the news about the contents of Bolton's book reinforces the case for calling witnesses.

"From the beginning, I've said that in fairness to both parties the decision on whether or not to call witnesses should be made after both the House managers and the President's attorneys have had the opportunity to present their cases," Collins said in a press release. "I've always said that I was likely to vote to call witnesses, just as I did in the 1999 Clinton trial. The reports about John Bolton's book strengthen the case for witnesses and have prompted a number of conversations among my colleagues." Romney told reporters "it's increasingly likely that other Republicans will join those of us who think we should hear from John Bolton," adding that "it's important to be able to hear from John Bolton for us to be able to make an impartial judgment."

Even Sen. Lindsey Graham (R–S.C.), one of Trump's most stalwart defenders, seemed to concede that Bolton's testimony might be relevant. "Let's see what's in the manuscript," Graham said. "Let's see if it's relevant, and if it is, then I'll make a decision about Bolton." But he coupled that suggestion with a demand that Joe and Hunter Biden also testify—a nonstarter as far as Democrats are concerned.

According to "associates" of Bolton interviewed by the Times, Bolton "believes he has relevant information, and he has also expressed concern that if his account of the Ukraine affair emerges only after the trial, he will be accused of holding back to increase his book sales." Unless two more Republicans join Collins and Romney in supporting a Bolton subpoena, it looks like he will profit from Trump's stonewalling and the incuriosity of GOP senators who are determined to acquit the president regardless of what the evidence shows.