Editor's note: This story has been updated with post-debate comments from the candidates' supporters.
HOUSTON — Billionaire Donald Trump is charging toward the Republican presidential nomination, and his two closest competitors showed they know it as they aggressively moved to halt his momentum in a scrum of a debate Thursday night.
At their 10th meeting on the debate stage, U.S. Sens. Ted Cruz and Marco Rubio scrambled to claim the anti-Trump mantle, unloading on the frontrunner with attacks both new and old. For Rubio, it was a relatively new posture after largely steering clear of the billionaire in previous debates. For Cruz, it was a return to fighting form that showed just how vicious things have gotten between the two candidates with five days until Super Tuesday.
"This guy's a choke artist, and this guy's a liar," Trump said of Cruz and Rubio at one point, giving way to a wild section of the debate that included Cruz urging Trump to "relax" and Trump firing back that Cruz is a "basket case."
From the first few minutes of the debate, Rubio made clear he would no longer duck Trump, going after the real estate developer over reports that he hired foreign workers to build some of his properties. The Florida senator later confronted Trump over repeating himself, one of several moments that led to loud chaos in the debate hall here at the University of Houston.
By the end of the debate, Cruz had caught up to Rubio in the crossfire with Trump, racking up a number of contentious exchanges with the billionaire that included some of his most personal insults yet. "You get along with nobody," Trump told Cruz, adding the Texas senator "should be ashamed of himself."
After the debate, even Cruz supporters admitted that Rubio proved himself an able ally in the fight against Trump. Both campaigns fielded questions from reporters about whether the two senators had coordinated beforehand, a theory their advisers dismissed.
"I think they both did a pretty good job of tagging the tail on the donkey," former Gov. Rick Perry told reporters.
Rubio's campaign was less conciliatory, with adviser Todd Harris saying the Florida senator accomplished what Cruz "has been trying to do unsuccessfully for months now," referring to effectively taking the fight to Trump. While Cruz's campaign said it welcomed Rubio's attacks on Trump, it also made clear it does not see Rubio benefiting as Trump bleeds support.
"Any votes that Donald Trump is losing tonight are not going to a member of the Gang of Eight," Cruz adviser Jason Miller told reporters, referring to the immigration reform legislation that is anathema to many primary voters.
Among the more fiery exchanges between Cruz and Trump was over the billionaire's tax returns, which he said he cannot release yet because he is being audited. Cruz pounced on that detail, challenging Trump to show his hand.
"If there's nothing, release them tomorrow," Cruz told Trump, questioning whether the billionaire had something to hide with a court case looming over his now-defunct Trump University. "I want you to think about that — having the Republican nominee on the stand in court about whether he committed fraud."
At one point, the clash between Cruz and Trump devolved into an extensive discussion of public polling, with each candidate citing specific surveys to argue they would be a stronger candidate in the general election. "He can't prosecute the case against Hillary," Cruz said of Trump, bringing up the billionaire's liberal stands and donations to Democrats.
Trump, Cruz's closest competition in his home state, scoffed at the idea he could not take on Clinton, citing a litany of polls. He made a point of mentioning he's "tied in Texas, by the way, which I shouldn't be."
"I know you’re embarrassed. I know you’re embarrassed," Trump told Cruz and Rubio, his voice dripping with condescension. "Keep fighting. Swing for the fences, man."
Cruz and Trump also clashed sharply on health care, with Cruz challenging Trump to own up to his statements on the issue that are out of sync with conservative orthodoxy. Trump did not comply, reiterating his position that he does not want people to die "on the sidewalk." "You may let it and you may be fine with it," Trump told Cruz.
Immigration dominated the debate early on, with a squabble breaking out between Cruz and Trump over who held which positions first. Cruz argued Trump could not be tough on the border because he gave money to Democrats who later teamed up with Rubio to push the "Gang of Eight" immigration reform legislation. Cruz charged Trump, known for his reality TV show series, with being MIA when it came time to stop the bill.
"In 2013, when I was fighting against the Gang of Eight amnesty bill, where was Donald?" Cruz asked. "He was firing Dennis Rodman on 'Celebrity Apprentice.'"
Cruz and Trump also had a confrontation over Cruz's criticism of Trump's sister's judicial record, which the Texas senator has characterized as pro-abortion. Trump suggested Cruz apologize to her, setting up an easy applause line for the Texas senator. "I will not apologize for a minute for defending the Constitution," Cruz replied.