On Sunday, The New York Times published a report widely described as a “bombshell” outlining leaks from the forthcoming memoir of former national security adviser John Bolton. The book, to be released in March and titled The Room Where It Happened, directly contradicts the core arguments of Donald Trump’s defense in the impeachment trial. According to the newspaper, in his book Bolton claims Trump told him in August 2019 “that he wanted to continue freezing $391 million in security assistance to Ukraine until officials there helped with investigations into Democrats including the Bidens.” Bolton’s manuscript also implicates other leading members of the Trump administration as having more knowledge of the Ukraine deal than they have admitted to, notably Secretary of State Mike Pompeo and Acting White House Chief of Staff Mick Mulvaney.

Congressional Democrats immediately used the report to prod Senate Republicans to call Bolton as a witness. The seven House impeachment managers issued a joint statement noting that what Bolton says he remembers “directly contradicts the heart” of Trump’s defense. They added, “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.”

Within hours of the report, Trump retweeted a denial. “I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens,” Trump asserted at the start a string of tweets that offered a factually inaccurate account of the Ukraine dispute. More ominously, Trump also retweeted two writers for The Federalist who denigrated Bolton, thus giving a likely preview of how the defense team will respond to Bolton’s claims. Sean Davis, one of the retweeted writers, claimed, “John Bolton is running the exact same revenge playbook against Trump that James Comey used. He’s even using the same agent and leaking to the same reporters. All because he’s mad Trump fired him for leaking and trying to start new wars. It’s so boring and predictable.”

Rudy Giuliani, Trump’s personal lawyer, made a statement to CNN that also took a jab at Bolton. “I believe that John Bolton only responds and pays attention to situations where he can invade or overthrow a government,” the former New York mayor said.

It’s true that Bolton is an unsavory warmonger, which itself should call into question Trump’s judgment in hiring him in the first place to be national security adviser. Moreover, the fact that Bolton is trying to profit from his time in the White House with a tell-all book rather than freely offering testimony also speaks ill of his character. Still, he was a witness to Trump’s actions in Ukrainegate and he’s directly contradicting Trump’s defense. The case for having Bolton testify under oath is beyond rational dispute.

But just because a course of action is the only logical thing to do is no guarantee that Senate Republicans will take it. In fact, Trump’s political opponents might be overestimating the ability of this bombshell to force elected Republicans to change their game plan. Susan Hennessey, a fellow at the Brookings Institution, argued, “This is game-changing to the political calculations.” Zac Petkanas, former aide to Hillary Clinton, concurred. “This is the smoking gun,” he argued. “GOP senators MUST vote to hear from John Bolton now. They have no choice.”

What might give Republican senators pause, however, and keep them loyal to Trump is that they are already strongly implicated in covering up Bolton’s testimony. They’ve sunk so much of their reputations and political prospects into Trump’s presidency, they can’t afford for it to go down now. Like a Wall Street bank, Trump has become too big to fail, so he always has to be bailed out.

Senate majority leader Mitch McConnell has already made it clear he’s working with the Trump White House to defend the president. This has a direct bearing on Bolton’s book and whether he will be called to testify in the Senate. Bolton’s publisher sent a manuscript of the book to the White House for security clearance. This means that Trump’s legal team, and their Senate allies like McConnell, have already had a chance to learn at least the basic outlines of Bolton’s claims.

As former Obama aide Ben Rhodes notes, the question now is, “What did McConnell—who admitted to coordinating Trump’s defense with the WH—know about what a potential witness knew?” Josh Marshall of Talking Points Memo observed that “McConnell working hand in glove with the President’s defense lawyers may now force some awkward questions.”

It’s still possible that four Senate Republicans will break ranks and give the Democrats the votes they need to take control of the impeachment trial. But in doing so, those Republicans would be making themselves the enemies not just of Trump but also of McConnell, who is now neck-deep in the scandal. Given McConnell’s institutional powers as Senate majority leader, they’d be putting their entire future in the Republican Party at risk.

Even if Bolton does testify, Sean Davis and Rudy Giuliani have already provided a script for rejecting his claims. The GOP can unify around the argument that Bolton is a disgruntled former employee, a Dr. Strangelove whom Trump fired for trying to start wars.

A more likely scenario is that the Republicans will continue to do what they’ve done for the last four years: serve as Trump’s body guards. They’ll do this because the cost of abandoning Trump, which would engulf the party in civil war, is too great.

If, as is likely, Republicans stick with Trump, Democrats have other means of getting Bolton’s claims on the public record. They could, for example, subpoena Bolton’s publisher and editors, whose testimony Trump can’t block with claims of executive privilege. In any case, Bolton’s book is scheduled to hit book stores by March 17.

If Bolton has released a bombshell, it’s one that will likely have a delayed effect. It almost certainly won’t lead to Trump’s removal. But it does further implicate Trump and his congressional allies, many of whom will, like Trump, face voters in November. The Bolton bomb, if it does go off, will be felt on Election Day.