I cannot keep up with Donald John Trump’s change of heart and mind.

He said this past summer that he’d be willing “100 percent” to talk to special counsel Robert Mueller about the “Russia thing” that has consumed the president’s attention.

Then he called Mueller’s probe a “witch hunt,” a hoax, a product of “fake news” and of Democrats who were upset at losing the 2016 presidential election.

Furthermore, he said he didn’t see a need to talk to the special counsel, given that there was “absolutely no collusion” with Russian hackers who sought to influence the 2016 election outcome.

Now … he is singing another tune. Today, the president said he would testify “under oath” if need be to Mueller and his team of legal eagles. He told reporters he would cooperate fully with Mueller’s team.

My head is spinning.

I certainly welcome the president’s latest declaration. If he is as innocent of wrongdoing as he says he is, then he would have no worried talking to Mueller, who clearly has a lot of questions to ask Trump.

Why did he fire FBI director James Comey? Did he pressure him to go easy on other close White House aides and advisers? Why didn’t he order his campaign team to tell the FBI that the Russians had “dirt” on Hillary Clinton they wanted to share with his campaign?

Those are just for starters?

If the president is going to maintain his pledge to talk to Mueller, my guess is that he’ll need to carve out a lot of time. The special counsel has a mountain of evidence to pore through and an equally high mountain of questions to get resolved.

But if the president is clean, there should be no problem.

I just can’t stop wondering if he is going to change his mind yet again and deliver a stiff-arm to the special counsel. Hey, the president is known to do such a thing.