How about that John Bolton?

The former national security adviser to Donald J. Trump once balked at testifying before Congress over whether the president committed impeachable offenses. Now he says he’s all in — if the U.S. Senate subpoenas him for an upcoming trial on whether Trump committed high crimes and misdemeanors.

This is a big deal, ladies and gentlemen.

At issue is whether Trump abused his power by soliciting a foreign government for a political favor and whether he obstructed Congress by blocking key aides from testifying. I believe he has done both things.

Now it’s Bolton, Trump’s former national security adviser who has said Trump’s supposedly “perfect phone call” to Ukraine’s president was fraught with peril. He now wants to testify to senators what he heard in real time, in the moment, with his own ears.

Trump doesn’t want him to testify. Why is that? Do you suppose that Bolton might offer testimony that damages the president’s case. Were he to offer exculpatory evidence — which would possibly clear Trump of wrongdoing — the president would be all in favor of Bolton speaking out. Isn’t that right? Um, yep. I believe it is!

Now comes the Big Question: If the Senate agrees to allow Bolton’s testimony, might he offer testimony that persuades moderate Senate Republicans to swing from clearing Trump to convicting him? Some observers think it’s possible. I am not so sure of that. The GOP fealty to Trump is so ingrained in its talking points that there might be no way for them to turn away from the president.

Oh, man, I hope I am wrong on that one.

However, it is beyond vital that we get the former national security adviser — the man with first-hand knowledge of what Trump said to Ukrainian officials — to tell the Senate what he knows.

Is this the game changer? Let John Bolton speak for the record and then we’ll know.