President Bill Clinton was impeached because he answered falsely to a question — posed before a grand jury — about whether he had a sexual relationship with a young White House intern.

Congressional Republicans were waiting for a reason to impeach the Democratic president. The president handed it to them by perjuring himself before a grand jury assembled by special prosecutor Kenneth Starr. Let’s remember that Starr’s probe began with an examination of a real estate matter involving the president and the first lady. We called it “Whitewater.” It was centered in Arkansas.

Somehow, though, it weaved its way toward the relationship the president had with a much-younger woman who was working in the West Wing.

Two decades later, a new special counsel, Robert Mueller, is conducting an investigation into Russian collusion, obstruction of justice and assorted other dealings involving — allegedly — Donald J. Trump.

I now am wondering if this current sex controversy involving Trump and a porn star is somehow going to end up on Mueller’s list of issues to investigate.

Trump has denied having an affair with this woman. Her lawyer has said on the record that the future president and his client did have a sexual relationship.

Given the sometimes-unpredictable nature of these investigations, I am left to wonder what might happen if he is able to subpoena Trump to testify before a grand jury he has assembled.

Is it at all possible that Mueller could ask Trump — who would be compelled to swear to tell “the whole truth and nothing but the truth” — whether he had an affair with this porn queen.

If Trump says “no,” and if the porn queen produces proof that she and Trump took a tumble in 2006, is that grounds for an impeachment?

Holy moly, man! Might history be capable of repeating itself?

Let’s all wait for all of this to play out.