Roast Master Rubio Photo: Sean Rayford/Getty Images

Marco Rubio has attacked Donald Trump as a fake conservative. He’s attacked him as a con man — a mogul whose only true art was that of the bankruptcy. But all of those substantive attacks on Trump’s inconsistent political positions and consistently unscrupulous business practices appear to have done little-to-nothing to erode the Donald’s support. So over the weekend, the Florida senator took a new tack and (apparently) solicited opposition research from some precocious fifth-grade bully.

“He’s always calling me ‘little Marco,’” Rubio said, while reading Trump’s Twitter feed at a rally in Virgina on Sunday. “I’ll admit he’s taller than me. He’s like 6’2’’, which is why I don’t understand why his hands are the size of someone who’s 5’2’’. Have you seen his hands? And you know what they say about men with small hands?”

Rubio’s supporters, realizing that their presidential candidate had just suggested that the other presidential candidate has an unusually small penis, roared with approval.

“You can’t trust ’em!” Rubio then shouted four or five times, to make clear that he hadn’t really “gone there.”

Trump is famously sensitive about his tiny paws, and has been ever since Spy magazine branded him a “short-fingered vulgarian” in the late eighties. But Rubio’s dig at Trump’s diminutive digits was only one of the senator’s many attempts at insult comedy over the weekend. Other highlights included:

“He doesn’t sweat because his pores are clogged from the spray-tan he uses. Donald is not gonna make America great, he’s going to make America orange!”

“Donald Trump likes to sue people. He should sue whoever did that to his face.”

“He’s flying around on Hair Force One!”

At the debate, “he asked for a full-length-mirror … maybe to make sure his pants weren’t wet.”

Rubio’s decision to bring himself down to the Donald’s level may be off-putting. But it’s not unreasonable for him to think he needs to fight garbage fire with garbage fire. Several political scientists have argued that Trump’s central appeal is his aura of authority and dominance. At a Jeb Bush rally back in February, MSNBC’s Benjy Sarlin spoke with a proud George W. Bush supporter who was leaning towards Trump this cycle. Explaining his reservations about Jeb!, the man pointed to the way the former Florida governor had withered under Trump’s attacks at the most recent debate. “If Jeb had told him to f—k off, he’d get my vote,” he said.

You can’t puncture a candidate’s aura of dominance with substantive attacks on his record. Thus, Rubio has opted to attack Trump as an over-tanned, ugly-faced, small-dicked pants-wetter, instead. The future of the Republican Party may ride on the strength of Rubio’s Don Rickles routine.