Chris Matthews has stepped in it. Big time.

The MSNBC “Hardball” host is taking intense social media fire over a remark he made over the weekend in which he likened Sen. Bernie Sanders’ big win in the Nevada caucus to the Nazi invasion and conquest of France during World War II.

One serious problem has emerged immediately after Matthews shot off his loud and boisterous mouth. Sanders, who is Jewish, lost many of his family members during the Holocaust.

Social media have gone berserk. Viewers are calling for Matthews, a veteran newspaper columnist, a former congressional aide and a longtime cable TV broadcast personality, to resign. Short of resignation, social media critics are calling on MSBNC to fire Matthews for his display of extreme insensitivity.

Here’s what I think ought to happen.

Chris Matthews needs to go on the air and issue an apology. And I don’t mean one of those phony “If I offended anyone” non-apologies. He needs to say something like this: “I made a terrible mistake. I am sorry for what I said. I engaged my motor mouth without turning on my sensitivity filter. I blew it and I apologize to everyone who heard me make that hideous comparison on the air.”

If the apology doesn’t stem the criticism, then he should quit. My hope would be that a full-throated, sincere apology might do the job.

What’s more, Matthews — who is known for his machine-gun delivery — needs to re-calibrate the manner in which he delivers his commentary.