Nancy Pelosi was right.

The Speaker of the House has not been present in the Senate chambers during the impeachment trial of President Trump, but Pelosi's presence looms large over the proceedings. And one of her most consequential choices in pursuing that impeachment — refusing to submit the Articles of Impeachment to the Senate until after the holidays — is bearing fruit: She wanted the Senate trial to include witness testimony, a prospect that seems much more likely now than it did just a few days ago.

Why? Thank John Bolton.

The New York Times on Sunday reported that Bolton, President Trump's former national security adviser, had written a book in which he says Trump told him he wanted to withhold military assistance to Ukraine until that country's officials there helped with an investigation into former Vice President Joe Biden. On Monday, the Times added that Bolton privately told Attorney General William Barr last year he was worried that Trump was granting personal favors to autocratic leaders.

Big stuff. So big, in fact, that Republicans who had seemed opposed to introducing witness testimony at the impeachment trial — preferring instead to rely wholly on arguments made by the president's lawyers and House impeachment managers — on Monday were starting to waver.

"The reports about John Bolton's book strengthen the case for witnesses and have prompted a number of conversations among my colleagues," Sen. Susan Collins (R-Maine) said in a statement. "It's important to be able to hear from John Bolton for us to be able to make an impartial judgment," added Sen. Mitt Romney (R-Utah). Sen. Lindsey Graham (R-S.C.) allowed that Bolton might be a relevant witness.

Even Senate Majority Leader Mitch McConnell (R-Ky.) was taken aback by the Bolton revelations. He was reportedly angry at being "blindsided" by news of the manuscript, which the White House had been reviewing since late December. McConnell put out a statement saying he "did not have any advance notice" of the Bolton manuscript.

In other words, the Bolton revelations have thrown a monkey wrench into the Senate's proceedings. Pelosi has to be pleased with herself.

Remember, she held onto the Articles of Impeachment for a very specific reason — using them as leverage to try to pressure McConnell into allowing new witnesses and testimony at the trial. McConnell, of course, conceded almost nothing. The Senate adopted trial rules that allowed for the possibility of witness testimony after the trial's opening statements, but that would require four Republicans joining Democrats to get a majority vote to include those witnesses. Pundits proclaimed that McConnell had beaten Pelosi in their personal power struggle.

But maybe she was playing a longer game.

The leak of Bolton's manuscript was conveniently timed — coming just as Trump's team was making its defense and the conclusion of the trial loomed near — so it is possible that the last-second revelations would always have become public at the last second, like something out of a movie.

Then again, it is also possible that Pelosi's delay bought just enough time for Bolton's manuscript to emerge at the perfect moment. Certainly, Pelosi would have been smart to buy that time no matter what — can you remember a month that has gone by in the last three years without some new Trump scandal hitting the front pages? Last month I predicted that new revelations of this president's wrongdoing will be dripping out, bit by bit, for years to come. If Pelosi delayed the impeachment trial hoping that something — anything — would emerge to hurt Trump's defense, she made a smart bet indeed.

None of this means that Trump will be removed from office. But the Bolton manuscript puts new pressure on those Senate Republicans — Collins, Romney, Lisa Murkowski of Alaska, and Lamar Alexander of Tennessee — who, rightly or wrongly, prize their reputations for independence and don't want to be seen rubber-stamping the president's acquittal. That, in turn, magnifies the absurdity of the "see no evil, hear no evil" stance adopted by so many of their GOP colleagues. The calculations are slightly different now for those Republicans who would like to escape history's wrath.

We haven't yet heard John Bolton's testimony. And it is fair to question whether Bolton, so long a controversial figure in American politics, is a reliable witness. For now, though, it appears that he has vindicated Speaker Pelosi's "go slow" approach to letting the Senate start the impeachment trial. But the trial still isn't finished. Who knows what revelations could still emerge?

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