Bernie Sanders is correct: The president of the United States is a liar. He might even be a pathological liar.

He has lied continually. He does it on purpose, which defines someone who lies.

Donald J. Trump needs to produce evidence to back up his latest lie, which is that “it is a fact” that Barack Obama ordered the wiretap of the president’s offices in Trump Tower.

He hasn’t done so. He didn’t produce any evidence of his previous lies. Not the Muslims cheering the Twin Towers collapsing on 9/11; or that Ted Cruz’s father might have been complicit in President Kennedy’s assassination; or the millions of illegal immigrants voting for Hillary Clinton.

He has lied every time he has said those things.

To “lie” is to willingly, knowingly tell a falsehood.

That’s what Sen. Sanders, I-Vt., has said. He stands by his statement. He is right. Trump is a liar.

And this is the guy who got elected president of the United States of America?

Spare me, please, the rejoinder that “all politicians lie.” Trump’s troops kept telling us that their guy “tells it like it is.” That’s different, presumably, from pure lies.

And also you may spare me the red herring that Bill Clinton “lied” about his affair with the intern, which got him impeached by the House of Representatives. I know that he lied under oath to the grand jury; I also know that was the ostensible reason for his impeachment. He paid his dues for lying.

Trump, though, hasn’t paid anything for these lies he has told. He got elected even as he lied his way all along the campaign trail.

He is lying now by suggesting that Barack Obama ordered the wiretaps.

And for that reason, Bernie Sanders should stand his ground.