Image copyright Reuters Image caption The tag-team hope their assault on Mr Trump will boost each of their chances of doing well on Super Tuesday

With the Super Tuesday primaries just a handful of days away, Donald Trump may be on the verge of becoming an unstoppable juggernaut barrelling towards the Republican nomination. But it was clear on Thursday night that two of his opponents in the political ring knew it - and weren't going to go down without a fight.

The presidential debate in Houston resembled a tag-team wrestling match, with Senators Ted Cruz and Marco Rubio taking turns trying every move in the book to pin their New York nemesis.

Meanwhile John Kasich appeared content to watch the contest from a seat in the stands, and Ben Carson wandered the concourse, looking for a door to the arena.

"Can somebody attack me, please?" Mr Carson requested at one point. No-one did.

When it came to Mr Rubio, Mr Cruz and Mr Trump, however, fists flew.

But was it too little, too late? It's a political truth that it's better to go after an opponent before people think you have to. And in a campaign that has placed authenticity above all else, the political expediency on display from two candidates who pulled their punches for much of Mr Trump's rise could prove their undoing.

If nothing else, however, Thursday night showed us the playbook for how the two senators are going to try to take down The Donald.

Here are their top five moves.

The business record slam

Media playback is unsupported on your device Media caption Marco Rubio takes aim at Trump's business credentials

Immigration was the subject of much of the early debate, and Mr Rubio launched the opening assault, accusing the New Yorker of relying on foreign workers to help staff his businesses in Florida.

"My mom was a maid at a hotel and, instead of hiring an American like her, you have brought in over 1,000 people from all over the world to fill those jobs instead," he said, executing a humble-roots, immigration-slam double-move.

Mr Rubio then offered a memorable line about Mr Trump's family wealth.

"If he hadn't inherited $200m, you know where Donald Trump would be right now?" Mr Rubio asked. "He'd be selling watches on the streets of Manhattan."

Mr Rubio also brought up Mr Trump's failure to release his tax returns and his "fake university", which has been embroiled in a fraud lawsuit that goes to trial later this year.

Tag-team partner Ted Cruz would take that up a bit later.

"I want you to think about, if this man is the nominee, having the Republican nominee on the stand in court, being cross-examined about whether he committed fraud," Mr Cruz said. "You don't think the mainstream media will go crazy on that?"

Mr Trump's defence: He said he hired foreign workers in his hotels for part-time jobs because he couldn't find Americans to fill them in "hot, hot sections of Florida".

Image copyright Getty Images

He said he would eventually release his tax returns once they'd been audited by the Internal Revenue Service, and boasted that he took a $1m loan from his father and turned it into $10bn.

And he called Mr Rubio a liar.

As for the university lawsuit, Mr Trump said he could have settled the frivolous case but wouldn't "on principle". And he noted how "awfully badly" he was beating Mr Cruz in the polls.

Was it a takedown? Yes. Trump supporters point to his business record as one of the reasons why he would make an effective president. Both Mr Rubio and Mr Cruz had Mr Trump rattled when they went after his supposed strength. This exchange happened early, and it set the tone for the rest of the evening.

The lack of policy lasso

Image copyright Reuters Image caption Mr Rubio repeatedly attacked Mr Trump, while the New Yorker called the Florida senator a liar

When the topic turned to healthcare, Mr Trump spoke about how as president he would push for allowing insurance companies to do business in multiple jurisdictions, removing "the lines around each state so we can have real competition".

Mr Rubio wanted to hear more.

"What is your plan?" he asked. "I understand the lines around the state, whatever that means."

He then put the squeeze on Mr Trump.

"This is not a game where you draw maps," he said - and went on to ask some version of the plan question another seven times, in a flurry of blows.

Mr Trump's defence: Line-removing was the extent of the plan, and when asked by CNN moderator Dana Bash if he'd like to add anything else, he declined.

"There is nothing to add," he said. "What's to add?"

And he mocked Mr Rubio for having a "meltdown on the stage" and sweating too much during the New Hampshire debate earlier in February.

"I thought he came out of the swimming pool," he said.

Was it a takedown? No. At this point, does anyone think that Mr Trump's supporters are backing him because they think he has detailed policy white papers? A one-point plan on healthcare is probably sufficient for a man who is running on attitude not aptitude.

The conservative credentials shiver

Image copyright Reuters Image caption Mr Cruz questioned Mr Trump's stance on healthcare and his history of giving money to Democratic politicians

Mr Cruz and Mr Rubio's next move was to question Mr Trump's conservative bona fides. Mr Cruz went after Mr Trump on healthcare, saying he supported liberal "socialised medicine".

"Did you say if you want people to die on the streets, if you don't support socialised healthcare, you have no heart?" Mr Cruz asked.

Mr Cruz also questioned Mr Trump's history of giving money to Democratic politicians and what that would mean when it came to nominating Supreme Court justices.

"Nobody who supports far-left liberal Democrats who are fighting for judicial activists can possibly care about having principled constitutionalists on the court," Mr Cruz said.

Mr Rubio joined in, noting that, until very recently, Mr Trump "was still defending Planned Parenthood".

And he added: "He says he's not going to take sides in the Palestinians versus Israel. These are concerning things."

Mr Trump's defence: He was happy to defend the moderate ground, saying that, as president, no-one would die on the pavements and streets.

He once again defended Planned Parenthood, saying that some of the services performed by the reviled-on-the-right women's health group are beneficial.

He also denounced Mr Cruz's rigid ideological dogmatism as impractical.

"We have to have somebody that's going to make deals," Mr Trump said.

Was it a takedown? No. Mr Trump embraced numerous positions that were thought to be political suicide for a Republican during the last debate, and he went on to win votes in South Carolina and Nevada by huge margins. Maybe his supporters don't believe the attacks. Maybe they view his unorthodox positions as yet another sign of his truth-telling authenticity. But when it comes to this move, Mr Trump is unbreakable.

The hypocrisy drop

Image copyright AP Image caption Mr Trump compared himself to Ronald Reagan, who took different positions on some key issues during his career

Trotting out examples of a candidate's hypocrisy is a classic debate move that's as predictable as it usually is effective.

When the foreign policy portion of the debate arrived, Mr Cruz launched a combo-drop of both Mr Trump and wrestling partner Marco Rubio - despite Mr Trump's past assertion that he opposed the Libyan intervention.

"In Libya, both of them agreed with the Obama/Clinton policy of toppling the government in Libya," he said. "That was a disaster. It gave the country over to radical Islamic terrorism, and it endangered America."

On immigration Mr Cruz said Mr Trump struts around the ring now, but he wasn't pushing the issue even a few years ago, when a reform bill was being debated in Congress.

"Where was Donald?" Mr Cruz asked. "He was firing Dennis Rodman on Celebrity Apprentice."

Image copyright AP

Mr Trump's defence: On immigration, he dodged and went after Mr Cruz personally.

"You don't have the endorsement of one Republican senator, and you work with these people," he said. "You should be ashamed of yourself."

He responded to the Libya question with flat denial.

"I never discussed that subject," Mr Trump said. "I was in favour of Libya? We would be so much better off if [Libyan leader Muammar] Gaddafi were in charge right now."

At one point Mr Trump compared himself to Ronald Reagan, who had taken different positions on some key issues over the course of his political life.

"Ronald Reagan was a somewhat liberal Democrat," he said. "Ronald Reagan evolved into a somewhat strong conservative. More importantly, he was a great president."

Was it a takedown? Yes. After Mr Trump's Libya response, Mr Cruz rolled with a well-prepared denouement that included a well executed website thrust.

"Donald just said that he never came out in favour of toppling Gaddafi in Libya," Mr Cruz said. "Well, he stated that in an interview that will be on our website, tedcruz.org.

"Maybe he forgot about it," Mr Cruz continued, "but I assume Donald will apologise where he sees that he said exactly that."

The bluster bash

Image copyright EPA Image caption Mr Rubio turned an attack on him back toward Mr Trump

Mr Rubio thinks he has Mr Trump's modus operandi figured out - and he took pains to explain it during Thursday night's debate.

"I see him repeat himself every night," Mr Rubio said. "He says five things. Everyone's dumb. He's going to make America great again. We're going to win, win, win. He's winning in the polls."

The move was set up in Mr Rubio's opening statement, in which he praised Mr Reagan and President George HW Bush, who was in attendance at the debate.

"For a generation, they defined conservatism as limited government and free enterprise and a strong national defence," Mr Rubio said. "But they also appealed to our hopes and our dreams. Now we have to decide if we are still that kind of party and still that kind of movement, or if we're simply going to become a party that preys on people's angers and fears."

Mr Trump's defence: What defence? Love him or hate him, this is the essence of Mr Trump's campaign, from stump speeches to debates.

Was it a takedown? Yes. It's a bit ironic that Mr Rubio would make the point that Mr Trump repeats himself, since he was so roundly criticised for programmatic repetition during the New Hampshire debate. But in that exchange Mr Rubio - the man the Republican establishment is turning to as their last hope - most clearly showed he can go toe-to-toe with Mr Trump and hold his own.

Of course if Mr Rubio had done that in the face of Chris Christie's attacks in New Hampshire, he might not have crashed to fifth place in that state's primary and this might have been a very different race.

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