Editor's note: This story has been updated throughout.
NORTH CHARLESTON, S.C. — Ted Cruz and Donald Trump, long allies in the Republican race for the White House, repeatedly turned on one another Thursday night in their most confrontational meeting yet on the debate stage — or the entire contest, for that matter.
Cruz, the U.S senator from Texas, and Trump, the billionaire businessman from New York, clashed most sharply on two fronts that have opened up as they emerged atop the GOP field: Cruz's eligibility to be president and Trump's conservative credentials. The showdown marked the most intense period of engagement so far between the two anti-establishment favorites, both of whom had refused to attack one another for months — an alliance that slowly crumbled as Cruz rose to the top of the polls.
"Well, I guess the bromance is over," Trump observed to reporters after the debate, blaming Cruz for blowing things up with his charge that the billionaire "embodies New York values."
By the end of the night, Cruz aides were claiming the senator had achieved the unachievable so far this election cycle: successfully taking on the unpredictable, bombastic Trump.
"For the first time this campaign, a candidate was able to go toe-to-toe with Donald Trump and win," Cruz adviser Jason Miller said after the debate. "It hasn't happened at any other point in this campaign."
The debate, the sixth this cycle and first of 2016, confirmed what Cruz has been musing about for weeks, according to campaign officials: The primary is a two-man race between himself and Trump.
The fireworks began early in the debate, when Cruz was asked about Trump's questioning of his eligibility to be president because he was born in Canada. Cruz started his response by noting that just a few months ago, Trump had said he had checked with lawyers and saw no problem with the issue.
“Now since September, the Constitution hasn’t changed, but the poll numbers have," Cruz said before noting that some of the more extreme theories about his citizenship would disqualify other candidates on the stage — including Trump, whose mother was not born in the United States.
“I’m not going to use your mother’s birth against you," Cruz told Trump. "You’re an American, as is everybody else on this stage.”
Trump disputed the notion that his poll numbers are on the decline, specifically in Iowa. "That was a misrepresentation," he told Cruz, a charge the survey-obsessed Trump would repeat again and again to reporters later Friday night.
Trump emphasized the concern he raised earlier this month — that the uncertainty surrounding Cruz's presidential eligibility could open him up to legal challenges from Democrats during the general election. Trump asked the audience to imagine what would happen if he won the nomination and made Cruz his running mate, only for the senator to get tripped up by the issue.
Cruz responded with a counteroffer, offering to make Trump his running mate. If Trump is right about him being ineligible for the presidency, Cruz told the billionaire, “you can get the top job at the end of the day."
Cruz seemed to outwit Trump in the citizenship exchange, though the billionaire delivered a solemn counterpunch later when the senator sought to tie him to the liberal politics of New York City.
Pressed to explain what he meant when he said Tuesday that Trump "embodies New York Values," Cruz ultimately described them as "socially liberal, pro-abortion or pro-gay marriage focused around money and the media." Cruz then referenced an interview Trump gave a few years ago in which he justified positions that are "very, very different from the views he’s describing now" by chalking them up to his residence in the solidly Democratic Empire State.
“Not a lot of conservatives come out of Manhattan. I’m just saying," Cruz concluded, riffing off a similar line from Trump that few evangelicals hail from Cuba, where Cruz's dad is from.
Trump countered Cruz's explanation of New York values by extensively invoking the 9/11 terrorist attacks and their aftermath, recalling the "smell of death" that he experienced firsthand. What Cruz said about New York was a "very insulting statement," Trump concluded.
"I don't think anybody should be attacking 20 million people, especially after the job they did" recovering from the attacks, Trump told reporters after the debate.
Cruz aides told reporters that Trump's invocation of 9/11 was a effort to obfuscate Cruz's argument that New York values are not exactly the most conservative. "I think many viewers knew exactly what Cruz was talking about," Cruz spokesman Catherine Frazier said.
Earlier in the debate, Cruz was asked about another controversy that has cropped up since the previous debate: a report from the New York Times on Wednesday that he did not properly disclose a loan during the 2012 U.S. Senate race. Cruz quickly turned the question on Democratic frontrunner Hillary Clinton, contrasting his financial situation at the time with her well-documented wealth.
“Unlike Hillary Clinton, I don’t have masses of money in the bank, hundreds of millions of dollars," Cruz replied, recalling the uphill battle he faced against the well-heeled David Dewhurst, then lieutenant governor.
Cruz eventually admitted he made a "paperwork error," revealing the loan on one form but not on another. But he did not stay on defense for too long, concluding his answer by taunting the newspaper loathed by conservatives.
“If that’s the best hit The New York Times has got, they better go back to the well," Cruz said to loud applause.
As the debate ended, things also got testy between Cruz and Senate colleague Marco Rubio of Florida, who accused the Texan of wavering on a range of issues from immigration to ethanol. "That is not consistent conservatism, that is political calculation," Rubio concluded.
Cruz, demanding a chance to respond to as many as "11 attacks" from Rubio, dismissed most of them as desperate. "I appreciate you dumping your oppo research folder on the debate stage," Cruz ultimately told Rubio, who shot back, "No, it's your record."
After the debate, Cruz aides called Rubio's barrage of allegations a desperate move. Somewhere in there, Cruz spokesman Rick Tyler said, Rubio "took the last breath of his campaign."