At Thursday night's Republican presidential debate in Houston, Sen. Marco Rubio (R-Fla.) finally came out swinging, and he finally landed some punches on Donald Trump, with Sen. Ted Cruz (Texas) acting as his wingman during important moments in the fight. There was yelling, there were insults hurled, there was taunting and belittling. It made for great TV.

Will Trump suffer in the polls or lose voters next Tuesday, on Super Tuesday, when 11 states vote in primaries and Alaska Republicans caucus? Maybe not — nothing seems to have hurt Trump so far. But you can bet that the Bernie Sanders and Hillary Clinton campaigns will be watching the results and studying Thursday's debate like a football team analyzing the footage of recent games of their upcoming opponent.

Trump is very probably going to be the Republican nominee, and for political scientists and pollsters and political strategists, his success is a riddle, wrapped in a mystery, inside an enigma, as Winston Churchill once said of Russia. If Rubio or Cruz is going to take Trump down, they need to experiment with what works when they face him in these increasingly gladiatorial debates. That's a godsend for the Democrats.

Here, for example, is an attack against Trump that worked. Rubio repeatedly demanded to know what Trump's policy prescriptions are: "What is your plan on your health care? You don't have a plan!" Rubio must have rehearsed at least part of this strike, but it didn't look robotic, which neutered Trump's counterattack that Rubio is the automaton who repeats himself. By pressing him on policy, Rubio craftily exposed Trump's lack of depth on important issues, but also appeared to have fun while doing it, giving at least as good as he got. Unlike Jeb Bush, Rubio looks convincing when he laughs off Trump's taunts:

Here's another extraordinarily pugilistic exchange, in which Rubio managed to hit Trump for paying a large fine for using illegal Polish labor, peddling products made in Mexico and China, bankrupting four companies, and running an allegedly scammy "fake" university. Fox News' Megyn Kelly called it an "opposition bazooka that Marco Rubio fired at Donald Trump":

Rubio threw so many things at Trump that Trump couldn't bat them away fast enough, but the one that really threw Trump off balance was the suggestion that he inherited his success instead of earning it. Weakness, noted.

Cruz was less successful in his attacks. So here's an example of what not to do:

After Trump called Cruz a "basket case" and told him to relax, Cruz responded, "I promise you, Donald, there's nothing about you that, that, that makes anyone nervous" — a show of bravado that would have been more believable without the stuttered "that" in the middle. And Cruz followed this up by griping about the rules, which never plays well in the audience.

The bigger flaw with Cruz's line of attack is that he largely focused on trying to paint Trump as a fake conservative by pointing to all the checks he has written to Democrats, and the poll numbers that show Trump losing to Clinton and Sanders. The Trump campaign couldn't have scripted a more helpful offensive.

As Trump pointed out in his towel-snapping riposte, Cruz shouldn't be talking about polls when he's losing so badly to Trump. More to the point, Trump has acknowledged donating to Democrats — and to Cruz — and even bragged about how easy it is to buy politicians. Cruz saying that Trump donated to Harry Reid and Hillary Clinton is just reinforcing Trump's narrative that Washington is corrupt and voters should choose somebody who isn't a politician — that leaves Trump and Ben Carson, and nobody thinks Ben Carson will get the nomination.

It's very likely that Clinton or Sanders will face Trump in the fall, and nobody really knows what that will look like. Trump doesn't play by the rules, but Democrats will have the advantage of studying the new rules that Trump has created for himself and, by extension, the 2016 presidential race. And as long as the Republican primary remains a three-man fight, the Clinton and Sanders camps can watch and learn from Cruz and Rubio's experiments in trying to weaken Trump.

What hurts Trump in the Republican primary won't be exactly the same things that damage him in a general election matchup. But already you can see some promising strategies to defang the GOP's likely nominee.

First, if you're going to attack Trump, hit first, armed with a smile and a briefcase full of material. Laugh off his insults and, as Rubio did, exaggerate his infractions (or inheritance) — if Trump is trying to explain, he's losing, or at least not attacking you. Second, make sure your attacks don't fit into Trump's narrative — people like him because he has as much contempt for politicians as they do, and he isn't a politician (once the election gets closer, voters may be more concerned about his lack of applicable knowledge).

The third and maybe biggest lesson so far is that you attack Trump where he's strongest, not weakest. "The most effective hits against Trump came on his business record (ironically, one of the only subjects in the debate where Trump possesses some actual knowledge)," notes Jonathan Chait at New York. "He appeared uncomfortable and offered weak defenses." Republican politicians may praise job creators, but Trump's angry voters are almost as irate at the New York financial elites Trump pals around with as they are Washington insiders.

Finally, the electorate may be in a sour mood, but they like a good show and a good laugh. Trump provides both, and Rubio joined the performance on Thursday night. Maybe along with studying Rubio's Trump attacks, Sanders and Clinton should sign up for improv comedy classes.