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When President Trump’s legal team unveiled its impeachment defense strategy on Saturday, the linchpin of the case was a small gap in the evidence. “Not a single witness testified that the president himself said that there was any connection between any investigations and security assistance, a presidential meeting or anything else,” said Mike Purpura.

This statement, while constructed in the narrowest possible fashion, was literally correct. A wide swath of evidence has established that the Trump administration attempted to trade diplomatic favors with Ukraine for investigations. Several aides testified, or communicated to each other at the time, that they understood this to be the policy. Trump demanded the investigations in public, implicitly dangled them in his phone call with Ukraine’s president, and his chief of staff Mick Mulvaney publicly confirmed the quid pro quo in a press conference. But every one of these pieces of testimony, in one form or another, fell short of the standard of (1) being sworn testimony (2) by a person who spoke directly to Trump and (3) heard him explicitly condition the meeting and aid for the investigations. It was like a jigsaw puzzle with a single piece missing, the picture completely apparent.

This vulnerability in the defense was already evident at the time. “Putting such an emphasis on ambiguities in Sondland’s testimony,” observed National Review editor Rich Lowry, “only makes sense if you are *absolutely certain* Bolton won’t testify.”

Well, so much for that.

Last night’s revelation that John Bolton’s forthcoming book reports the exact piece of evidence that Trump’s legal team insisted did not exist, that Trump specifically told Bolton that he was holding up the military aid in return for investigating the Bidens. Trump’s lawyers not only claimed this evidence did not yet exist, but called it one of the facts that “have not, and will not, change.”

Now it just might change. “The odds of deposition for new witnesses is certainly rising dramatically,” a senior Republican official confides to the Washington Post. “Before the Times report, GOP leaders were confident that they would defeat the vote this week. But now, it is less certain,” three GOP sources tell CNN.

Trump’s defenders frantically scrambled for a new improvised defense as to why Bolton must never testify. “The Democrat controlled House never even asked John Bolton to testify. It is up to them, not up to the Senate!” tweeted the president. The first sentence is false — the House did request Bolton’s testimony — and even if true, the second sentence would not follow. (Had the House erred by neglecting to summon a key witness, why compound the error rather than correct it?) Trump retweeted faithful defender Mollie Hemingway’s hope that Bolton was “overpromising and underachieving with their ‘bombshell’ anti-Trump book roll outs.” The apparent strategy here is to prevent Bolton from testifying and insisting he wouldn’t have had the goods anyway.

Meanwhile, other Trumpists like Sean Davis, Rudy Giuliani, and Lou Dobbs have tried out a new line of attack. Bolton is an embittered neocon who is taking revenge on Trump for refusing to start his desired wars by making up lies about the president, which happen to track closely with the sworn testimony of numerous other officials. This is a kind of omnibus Trump defense that has been applied to any incriminating testimony or leaks on any issue at all. The reasoning is a simple tautology: First, you make a refusal to testify against Trump a test of party loyalty, and then anybody who violates the test by definition is against your team and therefore biased.

If Bolton does testify, he not only refutes the linchpin of Trump’s defense, he also potentially implicates a wide array of other officials. According to the New York Times, Bolton’s book describes conversations with several other nervous Trump officials, including Mulvaney, Mike Pompeo, and William Barr, all of whom could then be asked to testify in turn. It reports that he “warned White House lawyers that Mr. Giuliani might have been leveraging his work with the president to help his private clients.” Giuliani of course is under criminal investigation, and was being paid by clients pursuing business deals in Ukraine, and who were themselves being paid by a key ally of Vladimir Putin. Even the most innocent interpretation of Giuliani’s role, combining profit-seeking with diplomacy, is a massive scandal on its face.

It is this potential that might, in the end, persuade Republicans not to allow Bolton to testify. Axios reports that Republican leaders will still try to prevent more testimony because “there is a sense in the Senate that if one witness is allowed, the floodgates are open.” A Republican aide explains, “If [Bolton] says stuff that implicates, say Mick [Mulvaney] or [Mike] Pompeo, then calls for them will intensify.”

There is a certain logic to this. Once you stop covering up Trump’s misconduct, pretty soon you end up confirming a lot of misconduct. Why, it’s almost as if they don’t actually think Trump is innocent.