Marco Rubio came to play.

The Florida senator delivered what was easily his best debate performance yet Thursday night, hammering frontrunner Donald Trump repeatedly on his character, his business record, and his claims to being a conservative. It was the performance he needed. The question now is whether it will matter at all.

Fresh off a three-state winning streak, Trump is close to being anointed the Presumptive Nominee by the media. With just days to go before the crucial sting of Super Tuesday primaries, Trump appears to be leading in most if not every state on the verge of a contest. He has the momentum. He has the math on his side.

He had a terrible night.

“Donald mentioned… that his position on immigration is what’s driven this debate,” Rubio said, leaping at his opponent after weeks of trying to play nice. “The truth is, though, a lot of these positions that he’s now taking are new to him.”

The man who has been compared to a robot, a guy unable to ever stray from his talking points, proceeded like the Terminator from there.

“In 2011, he talked about the need for a pathway to citizenship,” Rubio said. “In 2012, Donald criticized Mitt Romney, saying that Mitt lost his election because of self-deportation. And so even today, we saw a report... that Donald, you’ve hired a significant number of people from other countries to take jobs that Americans could have filled.” Rubio then referenced Trump’s use of Polish workers to construct Trump Tower, which cost the real estate mogul a major settlement in the early 1980s.

“My mom was a maid at a hotel,” Rubio continued. “And instead of hiring an American like her, you have brought in over a thousand people from all over the world to fill those jobs instead. So I think this is an important issue. And I think we are realizing that it’s an important issue for the country that’s been debated for 30 years, but finally needs to be solved once and for all.”

Trump, squinting and pouting as he stood between Rubio and Ted Cruz, responded with peculiar specifics about hiring practices in Florida.

Trump continued, “As far as the people I’ve hired in various parts of Florida during the absolute prime season, like Palm Beach and other locations, you could not get help. It’s the up season. People didn’t want to have part-time jobs. They were part-time jobs, very seasonal, 90-day jobs, 120-day jobs, and you couldn’t get. Everybody agrees with me on that. They were part-time jobs. You needed them, or we just might as well close the doors, because you couldn’t get help in those hot, hot sections of Florida.”

Trump, who had yet to really be attacked by Rubio—or, really, anyone else—this way, didn’t have much of a response when put on the spot. Trump seemed caught off guard by a candidate with whom he’d enjoyed a kind of détente for some time.

“If he builds the wall the way he built Trump Towers, he’ll be using illegal immigrant labor to do it,” Rubio said referring to Trump’s mythic planned wall at the border.

“Such a cute sound bite,” Trump responded like he was swatting away his since-departed favorite punching bag, Jeb Bush.

“It’s not a sound bite,” Rubio said, sticking to his guns. “It’s a fact. Again, go online and Google it. Donald Trump, Polish workers. The second thing about the trade war, I don’t understand, because your clothes and the ties you wear are made in Mexico and in China. You’ll be starting a trade war against your own clothes and suits.”

Rubio also prepared notes on Trump’s now defunct Trump University, for which the mogul may end up appearing as a witness in court to defend in the middle of the campaign season.

“A fake university!” Rubio, almost surprised at his own success, exclaimed. “There are people who borrow $36,000 to go to Trump University and they’re suing him now. $36,000 to go to a university.”

As Trump tried to respond, Rubio kept riffing on this same theme.

“That’s a fake school,” Rubio said. “And you know what they got, they got to take a picture with a cardboard cutout of Donald Trump. That’s what they got for $36,000.”

The old political rule is to attack your enemy’s strengths. And that’s exactly what Rubio was doing. Trump has framed himself as a brilliant businessman animated by his concern for the common man, the little guy, the silent majority. He’s never marketed himself as an orthodox conservative, but that’s where his opponents have hit him again and again with no result.

But Rubio tried something different with his attacks Thursday night. He tried to prove Trump is a huckster, a charlatan who doesn’t know what he’s talking about when pressed for specifics, a trust-fund baby looking to rip off hard-working Americans in order to make a dishonest buck. It went to the heart of Trump’s appeal, and for that reason it just might stick.

Rubio looked and sounded different from how we’ve ever seen him. But so did Trump. For a man who makes so many facial expressions, he rarely displays any recognizable human emotion, preferring instead to stay aloof and dismissive. Thursday night was different. He was, at turns, deeply frustrated and consumed by abject terror. Things were going very wrong, very quickly—and right before his squinty eyes.

Trump nervously leaned the full weight of his body onto the lectern and then tapped his fingers furiously at its sides. He leaned his head back to the right and pursed his lips tightly. He looked like a fish.

When Rubio spoke, Trump closed his eyes—as if to will Rubio to disappear from the stage altogether.

“You’re the only person on this stage that’s ever been fined for hiring people to work on your projects illegally,” Rubio said, pummeling him on the Polish workers issue.

Trump let out an exhausted sigh. His head seemed to sink into his shoulder pads. He grabbed the microphone with his left hand and wagged his finger with Rubio with his right. “No, no. I’m the only one on this stage that’s hired people,” he threw his arms out, “you haven’t hired anybody.”

As Rubio went on, Trump outstretched his hand at the moderators. “Excuse me, excuse me, excuse me, excuse me,” he pleaded, “he’s wrong!”

Rubio wouldn’t let up and Trump’s patience grew thin. “Be quiet,” he said while Rubio hammered him, “just be quiet.”

When Trump derided Rubio for not knowing “anything about business,” Rubio retorted, “I don’t know anything about bankrupting four companies!”

He smiled, and the crowd laughed.

Then, Trump started to get desperate. In fact, he started to sound like Ben Carson. “Excuse me! Hey, Wolf, let me ask you—am I allowed to respond?” he asked Wolf Blitzer. “You’ve been responding,” Blitzer said. Trump’s response was a frustrated gurgle. “No, I haven’t!” he said, “I really haven’t. I haven’t.”

Trump tried to attack Rubio for his personal financial troubles, but it didn’t stick. Rubio countered with mockery. “Here’s a guy that inherited $200 million,” he said. “If he hadn’t inherited $200 million do you know where Donald Trump would be right now? Selling watches in Manhattan!”

As Rubio grilled him, Trump cried, “No, no, no, no! No, no, no!” He threw his hand out, “that is so wrong!”

After Trump reminded the audience that Rubio had recently been roasted by erstwhile candidate Chris Christie, Rubio pressed Trump for specifics on his health-care plan. Trump talked in circles, claiming he would magically create competition by “removing” the “lines around the states,” and then claiming it over and over again.

Rubio gestured to Trump, “Now he’s repeating himself,” he smiled.

The audience cheered. They got the joke—Rubio’s robot reputation stems from his habit, most clearly shown at his disastrous pre-New Hampshire primary debate, of hewing to his talking points when flustered. Trump stuck his finger in the air in defiance, “no, no, no!” he said, “no no no! I don’t repeat myself! I don’t repeat myself!”

—with additional reporting by Gideon Resnick