Donald J. Trump Sr. was in full rant mode in Billings, Mont., earlier this week.

He went to Montana to stage a campaign rally and then launched into a bizarre riff about the possibility of his being impeached by the U.S. House of Representatives. He mentioned Rep. Maxine Waters, the Democrat who vows that Trump will be impeached. “I’m doing a great job,” Trump bellowed, wondering how he could be impeached even though his presidency — he says — is the most successful in the history of the republic.

Trump seems to assert that a president who does a “great job” shouldn’t be impeached. We can debate until hell freezes over whether Trump is doing anything approaching a great job. We’ll save that one for another day.

However, let’s review a bit of recent history … shall we?

President Bill Clinton also was doing a great job during his second term in the White House. The economy was on fire. We were heading toward a balanced federal budget. Joblessness was low. Times were good.

Then the president committed what Republicans believed was an impeachable offense. Special prosecutor Kenneth Starr was conducting a wide-ranging investigation that turned up a relationship that the president had with a young White House intern, Monica Lewinsky.

Starr summoned the president to talk to a grand jury, which then asked him about the relationship. The president who took an oath to “tell the whole truth” didn’t tell the truth. He committed perjury.

Boom! There you have it! Republicans had their impeachable offense!

The House impeached the president who was doing a “great job.” Clinton went to trial in the Senate. He was acquitted on all charges.

So … for the current president to suggest that he shouldn’t be impeached because he’s doing a “great job” is to ignore recent political history.

Donald Trump well might be found to have committed an impeachable offense. Impeachment, let us remember, has nothing to do with the president’s performance in office. It has to do with conduct.