SALEM, Va. — "He's 6'2," Marco Rubio said of Donald Trump Sunday night, "which is why I don't understand why he has hands the size of someone who's 5'2. You know what they say about men with small hands."

It was perhaps the most explicit small-penis joke in the history of presidential politics.

Rubio has crawled into the mud with his vulgarian opponent. This may be necessary if he is to beat Trump, but it clearly carries dire risks for a man who wants to come across as presidential.

"I liked him until he got down in the mud with Trump," Paul Eveland told me before the Rubio rally. While his wife, Ceci, is behind Rubio, Paul is undecided. Ceci granted that point: "It's disrespectful to the office."

Donald Lawrence calls Trump "a damn clown. I used to watch people like that on cartoons." But Lawrence, who was dragged to the rally by his wife, a Marco fan, doesn't appreciate Rubio's style of fighting the clown Trump. "It kinda made them look like they were a big joke," said Lawrence. "You get somebody who wants to joke around, you wonder who good a president they'll be."

Since the Thursday debate in which Rubio took Trump down a notch through mockery and Trumpesque interruptions, Rubio has included his trash-talk stand-up routine. At every rally, Rubio has mocked Trump in a style similar to Trump's attacks on the other Republican candidates — personal, and at times vulgar. While Trump mocks Rubio as short and sweaty, Rubio mocks Trump as a spray-tanner and a pants-wetter.

Thursday night was Rubio's first on-stage penis joke about the front-runner.

"I hate to put it this way," Jonathan Tarris said, "but you have to stoop to Trump's" level. After the rally I asked Tarris about the penis joke. "It was funny. It was funny. It might have been a little bit — inappropriate. But I laughed."

His girlfriend, Kayla Sawyer, agreed. "It was funny."

Many Republicans, desperately hoping for someone who can battle Trump, applaud Rubio's tactics.

Mike Teal is a retired furniture maker. He calls Trump "a con artist" and backs Rubio. "He's taking Trump on right now," Teal said before the rally. "I give him a lot of credit."

Dana Bledsoe, who calls herself something of a "moderate" Republican, loved Rubio's debate performance. "I thought he did a great job throwing punches at Trump ... and he kept himself collected — didn't get flustered."

Rubio nearly apologized to the crowd on a couple of occasions amid his stand-up routine. "Give me a couple of more minutes to have fun with it," Rubio said after about five minutes of the mockery, "and then I'll get to the policy, I promise."

"I like debates about ideas" and policies, Rubio said at one point. "But you cannot have a policy debate with someone who has no policies."

Rubio ties some of his attacks on Trump to Trump's fitness for the presidency: "Donald Trump is trying to carry out the biggest scam in American political history" is a standard Rubio line these days. "A scam is when you try to take advantage of people who are hurting," Rubio said Thursday, before making a slight attempt to appeal to Trump's supporters: "There are people hurting in this country," Rubio said, referring briefly to wage stagnation, and railing against student-loan debt.

Timothy P. Carney, The Washington Examiner's senior political columnist, can be contacted at tcarney@washingtonexaminer.com. His column appears Tuesday and Thursday nights on washingtonexaminer.com.