One of the curious facts about the Republican primaries is that the candidates have been reluctant to go after Donald Trump until they had no other choice—and by then, it’s been too late. Usually it’s only when a candidate is sinking in the polls that he starts aiming potshots at the-real estate mogul, as Jeb Bush did over the protracted slow death of his campaign. Ted Cruz has been willing to attack Trump on the campaign trail and through ads, but until recently kept up a smarmy pretense of liking his friend Donald, hoping to inherit his votes after he somehow withered away. Marco Rubio, even more strikingly, has shrunk from a fight with the frontrunner altogether. 

That all changed dramatically with Thursday night’s debate in Houston, with Cruz and especially Rubio hammering away at Trump’s vulnerabilities: his unwillingness to show his tax records, the lawsuits against the allegedly fraudulent Trump University, his history of supporting liberal positions and policies, and his glaring lack of specific policy knowledge. 

Rubio in particular came out looking better than he has in recent debates—and his animated performance has been getting rave reviews, even from Cruz backer Glenn Beck. Rubio earned himself the “MarcoBot” monicker in his disastrous New Hampshire debate performance for repeating his talking points endlessly. Thursday night, he inverted that meme, effectively mocking Trump for repeating the same tired catchphrases about solving health care by introducing more competition—and leaving Trump flustered.

Rubio tripped Trump with a simple question: “What is your plan?” Trump got increasingly fazed:

RUBIO: ... What is your plan, Mr. Trump?

(APPLAUSE)

RUBIO: What is your plan on healthcare?

TRUMP: You don’t know.

BASH: (inaudible)

TRUMP: ... The biggest problem...

(CROSSTALK)

RUBIO: ... What’s your plan...

TRUMP: ... The biggest problem, I’ll have you know...

RUBIO: ... What’s your plan... 

TRUMP: ... You know, I watched him melt down two weeks ago with Chris Christie. I got to tell you, the biggest problem he’s got is he really doesn’t know about the lines. The biggest thing we’ve got, and the reason we’ve got no competition, is because we have lines around the state, and you have essentially...

RUBIO: ... We already mentioned that (inaudible) plan, I know what that is, but what else is part of your plan...

TRUMP: ... You don’t know much...

RUBIO: ... So, you’re only thing is to get rid of the lines around the states. What else is part of your healthcare plan...

TRUMP: ... The lines around the states...

RUBIO: ... That’s your only plan...

TRUMP: ... and, it was almost done—not now...

RUBIO: ... Alright, (inaudible)...

TRUMP: ... Excuse me. Excuse me.

RUBIO: ... His plan. That was the plan...

TRUMP: ... You get rid of the lines, it brings in competition. So, instead of having one insurance company taking care of New York, or Texas, you’ll have many. They’ll compete, and it’ll be a beautiful thing.

RUBIO: Alright...

(APPLAUSE)

RUBIO: So, that’s the only part of the plan? Just the lines?

BASH: (inaudible)

TRUMP: The nice part of the plan—you’ll have many different plans. You’ll have competition, you’ll have so many different plans.

RUBIO: Now he’s repeating himself.

TRUMP: No, no, no.

(LAUGHTER) (APPLAUSE) (CHEERING)

But did the long-delayed attack on Trump come too late to revive Rubio’s faltering campaign? The Florida senator still has a path to the nomination, but it is a narrow one. With Jeb Bush out of the race and Rubio’s strong performance on Thursday, the money should come pouring into the coffers from the donor class that’s been desperate for an anti-Trump champion. If Trump’s rise is blunted on Super Tuesday—most likely by losing Texas to home-state Senator Cruz—Rubio will have enough breathing room to revive his campaign in the remaining states, many of them theoretically friendlier to his style of politics, and could score a big win in Florida on March 15. But everything—everything—has to go his way. And he’ll have to keep hammering Trump, day after day, the way he did on stage in Houston. 

At least he’s now shown that he’s capable of it. Prior to Thursday’s debate, the thought of the nervous, seemingly fragile Rubio going up against master bully Trump seemed like an epic mismatch on par with chess player Bobby Fisher going against Muhammad Ali or Bambi fighting Godzilla. Yet Rubio held his own. 

Consider this exchange about Trump’s business practices:

TRUMP: But you wouldn’t know anything about it because you’re a lousy businessman.

RUBIO: Well, I don’t know anything about bankrupting four companies. You’ve bankrupted..

TRUMP: No, I—and you know why? You know why?

(APPLAUSE)

RUBIO: I don’t know anything about...

TRUMP: You know why?

RUBIO: ... starting a university, and that was a fake university.

BLITZER: One at a time.

TRUMP: First of all...

BLITZER: One at a time.

TRUMP: ... first of all, that’s called a...

RUBIO: There are people who borrowed $36,000...

BLITZER: Hold on. One at a time, Mr. Trump.

RUBIO: ... to go to Trump University, and they’re suing now—$36,000 to go to a university...

TRUMP: And by the way—and by the way...

RUBIO: ... that’s a fake school.

TRUMP: ... and by the way...

RUBIO: And you know what they got? They got to take a picture with a cardboard cutout of Donald Trump...

TRUMP: ... I’ve won most of the lawsuits.

RUBIO: That’s what they got for $36,000.

BLITZER: All right, I want to move on.

TRUMP: And they actually did a very good job, but I’ve won most of the lawsuits.

BLITZER: Mr. Trump, Senator, I want to bring in...

RUBIO: Most of the lawsuits.

This wasn’t a clear-cut victory for Rubio, however. Many, if not most, Trump fans have an intense empathetic attachment that will cause them to stick with him no matter what. His loyalists will feel that he held his own simply by staying aggressive and insulting even when he was—for the first time—genuinely put back on his heels at moments. Still, Rubio succeeded in introducing Republican voters to the idea that Trump is not the great businessman he claims to be. It’s the kind of nagging doubt that might help to finally put a ceiling on Trump’s support and give Rubio the extra time he needs. 

But now that Rubio has gone on the attack, the question is whether he can survive the inevitable counterattack. Trump has hitherto largely ignored Rubio, but if the past is any guide, Rubio will now be in Trump’s crosshairs. 

If Rubio does turn the odds around and win, Thursday night will be seen as the turning point. The problem is that Trump could continue to steamroll through the primaries, which will prove only that Rubio waited too long to go after him.