US Election 2016: Cruz and Rubio attack Trump in debate
Republican presidential hopefuls Ted Cruz and Marco Rubio have unleashed a barrage of attacks on front-runner Donald Trump in the last debate before next Tuesday's pivotal US primaries.
Immigration, healthcare and outreach to Latino voters dominated the debate, which disintegrated into long periods of shouting and personal insults.
Mr Trump has won three of the first four contests held so far.
Next week's vote in 11 states is held on what is known as Super Tuesday.
The three men are seeking to be named as the Republican candidate in November's presidential election.
Analysis: Anthony Zurcher, BBC News North America reporter
At long last the Republican candidates have come to the realisation that Donald Trump can actually win this race, but it may be too late.
For more than two hours, Senators Marco Rubio and Ted Cruz took turns throwing punches at the New Yorker. They attacked him on his business record; they mentioned hypocrisy; they questioned his conservative credentials; and they criticised the lack of detail in his policies and his reliance on bluster.
"We're having a lot of fun up here, aren't we?" the front-runner quipped at one point. But the truth is that Mr Trump was on his heels for much of the evening.
The challenge for the men who would unseat the leader, however, is that the best time to bludgeon a candidate is before it is clear circumstances are forcing you to act. In a campaign where authenticity is worshipped above all, Thursday's fireworks could smack of the kind of political expediency many associate with traditional politicians.
Both Mr Cruz and Mr Rubio drew blood with their attacks but Mr Trump will be likely to emerge unbowed.
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Mr Rubio, who has come second in several recent contests, mounted a series of attacks on Mr Trump.
"If he hadn't inherited $200m, you know where Donald Trump would be?" Mr Rubio said in one tense exchange. "Selling watches in Manhattan."
Mr Rubio also criticised Mr Trump's failed online education venture, Trump University, and assailed him for hiring foreign workers rather than Americans in his construction projects.
Mr Trump shot back: "I hired tens of thousands of people. You've hired nobody."
The billionaire real estate mogul found himself increasingly on the defensive about his business dealings and his conservative credentials.
In other exchanges
- Mr Cruz said Mr Trump's reputation as a dealmaker meant he could not be trusted to appoint conservative justices to the Supreme Court; Former neurosurgeon Ben Carson said: "the fruit salad of their life is what I will look at" - explaining this included everything SC candidates had done in their lives
- Most of the candidates were asked about releasing their tax returns; Mr Cruz and Mr Rubio pledged to release them in days, while Mr Trump demurred
- Moderator and Telemundo presenter Maria Celeste grilled Mr Trump on how he would appeal to Latino voters in the presidential election
- Mr Trump addressed criticisms from Mexico's former president, who said Mexico would never pay for a border wall between the two countries. "Mexico will pay for the wall," Mr Trump said. "The wall just got 10 feet taller"
- Ohio Governor John Kasich touted his successes in his state, including overcoming a budget deficit and bringing new industries
- Mr Carson, struggling to participate, at one point called out: "Can someone attack me?"
The fruit salad of their life is what I will look at.
Trump on Rubio: "This guy's a choke artist [not able to deliver on stage]."
Rubio to Trump: "You're a lousy businessman."
"If he hadn't inherited $200m, you know where Donald Trump would be right now, selling watches in Manhattan."
Trump to Cruz: "This guy is a liar."
Cruz response: "Falsely accusing someone of lying is itself a lie, and it's something Donald does daily."
Trump to Cruz: "You get along with nobody. You don't have one Republican senator backing you. Not one…You should be ashamed of yourself."
"I know you're embarrassed."
Rubio to Trump: "You're the only person on this stage that's ever been fined for hiring people to work on your projects illegally."
Trump response: "I'm the only one on the stage that's hired people. I've hired tens of thousands of people over my job. You've hired nobody. You've had nothing but problems with your credit cards."
Mr Trump has been extremely popular despite his controversial comments about deporting millions of undocumented workers and banning Muslims from travelling to the US.
He is currently leading in 10 out of 11 states holding contests on Super Tuesday when a quarter of the total numbers of delegates needed to secure the Republican nomination will be up for grabs.
He has 82 Republican party delegates, Mr Cruz has 17 and Mr Rubio has 16. To become the Republican party's nominee, a candidate has to have 1,237 total state delegates.
On the Democratic side, Hillary Clinton and Bernie Sanders will compete for 1,004 delegates on Super Tuesday.
Mrs Clinton has a clear lead with 505 delegates, but the majority are super delegates who can change their mind during the course of the campaign. Mr Sanders has secured 71 delegates in the first three races.
Each party formally announces its presidential candidate at conventions in July, four months before the presidential election.
Key dates to come
27 February - South Carolina primary (Democratic)
1 March - "Super Tuesday" - 15 states or territories decide
18-21 July - Republican convention, nominee picked
25-28 July - Democratic convention, nominee picked
8 November - US presidential elections