It’s a tantalizing thought for those who wish the Senate had convicted President Donald Trump at his impeachment trial in January: If only former national security advisor John Bolton, whose new book makes sensational accusations against the president, had testified before either the House or the Senate, Mike Pence might be president.

Tantalizing, but almost certainly false.

In “The Room Where It Happened: A White House Memoir,” Bolton apparently provides new evidence that Trump conditioned security aid for Ukraine on an agreement by that country to help dig up dirt on former Vice President Joe Biden.

The Washington Post quoted Bolton as saying that Trump “wasn’t in favor of sending them anything until all Russia-investigation material related to (Hillary) Clinton and Biden had been turned over.”

There are two “if only” narratives about Bolton and impeachment.

One suggests that the outcome of impeachment might have been different if only House Democrats hadn’t rushed to impeach Trump without subpoenaing Bolton and waiting for the courts to decide whether he had to comply.

According to The New York Times, Bolton himself makes a variation of this argument in the book. It reported that Bolton “had nothing but scorn for the House Democrats who impeached Mr. Trump, saying they committed ‘impeachment malpractice’ by limiting their inquiry to the Ukraine matter and moving too quickly for their own political reasons.”

After declining to testify before the House until his legal scruples had been addressed, Bolton later decided that he would testify at Trump’s Senate trial if he were subpoenaed.

That brings us to the other “if only” theory: that if only Senate Republicans had agreed to allow witnesses at the trial, Trump might have been convicted and expelled from the White House.

But that’s also a fantasy. Despite pleas, the Republican Senate rejected hearing witnesses even after Bolton said he would testify if subpoenaed.

Even now, Republicans aren’t rushing to express regret that Bolton didn’t testify. Sen. Lamar Alexander of Tennessee told the Washington Post that he wasn’t second-guessing his votes to reject witness testimony and acquit Trump.

“I said he did it,” Alexander said, referring to Trump’s attempt to have Ukraine investigate Biden. “I was convinced. I didn’t need any more evidence.”

Whether or not they agreed with Alexander that Trump “did it,” the vast majority of Republican senators weren’t going to vote to oust a president popular with the party’s base. In the end, the only Republican voting for conviction was Sen. Mitt Romney of Utah.

It’s impossible to believe Bolton’s testimony, no matter how incriminating, would have made a difference. Now as before Bolton’s book, the only way Trump will be removed is at the ballot box.

Michael McGough is the Los Angeles Times’ senior editorial writer, based in Washington, D.C.