OKLAHOMA CITY — It was the biggest crowd Sen. Marco Rubio (R-Fla.) had gotten in this state, more than 1500 voters filling the floor of a downtown event center to hear him. And for 10 minutes, that crowd laughed along with Rubio as he warned them to not “lose the conservative movement to a con man.” Some voters were more than ready, interrupting Rubio’s wind-up about how he defeated Florida Gov. Charlie Crist with shouts of Trump’s name.

“These guys are taking away my punchlines!” Rubio said. “I ran then because I believe that ours was the party of Reagan, and the conservative movement is the way forward for America. I was not going to let a con man take over.”

As in Dallas, where his extended riff on Trump’s spelling, wealth, age and bladder control turned viral, Rubio used the Oklahoma City speech to humiliate the front-runner.

“The only loan I ever started out with was a student loan, which I just paid off four years ago,” Rubio said. “He has spent a career in business, 50 years, sticking it to the little guy.”

While Rubio attacked Trump, national cable networks played his speech live — a favor granted constantly to Trump, rarely to anyone else. When Rubio switched tacks to deliver his positive stump speech, the networks cut away. In miniature, if a rally of almost a thousand people can be called miniature, it was a demonstration of the struggles Rubio has before Super Tuesday and of the potency these arguments may have when the race moves on.

Belatedly, Rubio’s campaign has started to resemble the one that propelled Mitt Romney past a duo of insurgents. In 2012, Romney recovered from setbacks in South Carolina (where he lost to Newt Gingrich) and the Minnesota and Colorado caucuses (where he lost to Rick Santorum) with strong debate performances and an air assault by his Restore Our Future Super PAC. Rubio’s Oklahoma rally was just one of three he would be holding before the vote; a victory in any state would defy the expectations set both by Trump and by the frustrated campaign of Sen. Ted Cruz (R-Tex.), which hopes to contrast its expected Texas win with a wipeout for Rubio.

According to Politico’s Ken Vogel, the pro-Rubio Conservative Solutions PAC has vacuumed up $20 million since Bush left the race and the anti-Trump flamethrower was passed to Rubio. In the 72 hours before the polls open, $6.4 million has been reserved for spots that attack Trump on topics such as foreign policy ignorance, eminent domain and kicking disabled veterans off of his property. They complement a push from the American Future Fund in which three disgruntled graduates of Trump University, Trump's pricey real estate seminar, say they were scammed.

All of the ads hit themes that conservative thought leaders had been writing about for months. None are obvious blockbusters. In some large Super Tuesday states, such as Texas and Georgia, early voting began before these ads ran.

But in his current messaging, which is being fine-tuned from stop to stop Rubio casts Trump as not only an imbecile but a rip-off artist and a wimp.

“He acts like he’s some sort of tough guy,” Rubio said. “This isn’t a tough guy. The other day he told a protester, ‘I wish I could punch you in the face.’ Donald Trump has never punched anyone in the face, okay? This guy was born into money, inherited $200 million — he’s never punched anyone in the face! He’s not a tough guy!"

Attacks like that, which were warmly received in Dallas, drew hooting and cheers in Oklahoma. After the speech, however, it was easy to find voters who disliked Trump but hesitated to embrace the attack lines.

“I don’t think he really needs to take on Trump,” George Colbert, 68, said. “I like Rubio because he’s Rubio.”

Years of research on political attack ads, and on negative politics, suggest that this reaction is typical. Voters are reluctant to say that they like negative campaigning, but they process it and let it inform their votes.

Negative campaigning has an echo effect, too: It can produce free media coverage of the subject being attacked. Although Rubio’s Trump riff accuses “the media” of protecting the front-runner in order to destroy him in the fall, his most damaging lines are based on deep reporting about Trump’s business failures.

The Rubio and American Future Fund attacks on Trump University have inspired fresh coverage of the ongoing legal case against it. Trump’s operation has looked only slightly more prepared for the topic than his opponents, with a lawyer answering questions from CNN by providing 14 affidavits from satisfied Trump University customers.

And the scale of Rubio’s challenge was evident just hours later, when a much larger crowd filed into the Cox Convention Center, half a mile away. A significant reeducation campaign would need to be implemented before they stopped thinking of Trump as a bar-brawling friend of the working man. Asked about the Rubio attacks, Trump supporters either said the endorsement of Trump by Gov. Chris Christie (R-N.J.) overwhelmed them, that Rubio was irrelevant or that they hadn’t even watched the debate.

“Rubio won’t even win his home state,” said Mark Morris, 57. Trump, by contrast, reminded him of the Oscar-winning film “Gladiator,” and of Russell Crowe’s hero Maximus. “He survives the battle, and the emperor calls him in. The emperor says, ‘I need you to go to Rome.’ Maximus says, ‘I've never even been to Rome.’ He says, ‘That's why I want you to go. It’s corrupt there.’ That was so profound, so profound.”

Robert Jay, 28, a lineman who was kept from voting by an old felony conviction, did not watch the debate. Wearing a T-shirt with the slogan “white pride worldwide,” he explained that he bought it “as a response to Black Lives Matter,” and was happy that his wife, a onetime supporter of President Obama, was casting the family’s vote for Trump.

“He’s tough — I don’t know what Rubio is talking about — and he says if you attack us, we’re going to attack you,” Jay said. “We'’re going to be strong. And that’s important.”

Marco Rubio’s rise to prominence

NATIONAL HARBOR, MD- MARCH 5 : Sen. Marco Rubio (FL) speaks at the Conservative Political Action Conference (CPAC) at the Gaylord National Resort & Convention Center on Saturday, March 5, 2016 in National Harbor, MD. (Photos by Amanda Voisard)