NORTH CHARLESTON, S.C. — Donald Trump and Sen. Ted Cruz of Texas sharply and at times comically attacked each other Thursday night over the Canadian-born Cruz's eligibility to be president, shedding months of cordiality as the latest Republican presidential debate became a hand-to-hand fight in their razor-close contest in the Iowa caucuses.
The ferocious back-and-forth marked the end of a de facto non-aggression pact, presaging a new phase of the campaign in which the two leading candidates, both seeking support from hard-line conservatives, can be expected to increasingly turn their fire on each other.
Cruz, who has gained ground against Trump recently in Iowa, where they are now virtually tied in the polls, charged that Trump was turning desperate because his standing as the leader of the Republican field had turned shaky. Cruz, who for months was Trump's closest ally in the race, noted that Trump had not joined others in the fall in trying to make an issue out of Cruz's birth to an American mother living in Calgary, Alberta.
"The Constitution hasn't changed, but the poll numbers have," Cruz said. "Donald is dismayed that his poll numbers are falling in Iowa." Cruz added that the law was on his side, noting that Sen. John McCain, while born in Panama, was eligible to run for president. By Trump's standard, Cruz asserted, Trump himself might not be eligible to run for president because his mother was born in Scotland.
"But I was born here — big difference," Trump said.
Their exchange escalated quickly, with Trump drawing boos and jeers from the audience here as he sought to defend himself by bragging anew about his poll numbers. "I'm beating you," Trump said. "I think I'm going to win fair and square."
Cruz delivered his most aggressive performance in the six Republican debates so far as he sought to protect the political support he has built among social conservatives and evangelical Christians. He was relentless in trying to put Trump in his place, a move aimed in part at appealing to establishment Republicans who are deeply uncomfortable with Trump's candidacy and whom Cruz has started to court.
For several moments, the debate turned from a reality show into a comedy as Trump mused that if he chose Cruz as his running mate, Democrats would sue to challenge Cruz's eligibility — as they would if Cruz won the presidential primary.
"If you become the nominee, who the hell knows if you can even serve in office?" Trump said.
Cruz, a pugnacious, polished debater as a Princeton undergraduate, gave no quarter.
"I'm not going to take legal advice from Donald Trump," he said to laughter. And he offered to make Trump his running mate, so he could assume the presidency if a theoretical legal challenge against Cruz's eligibility were successful.
Trump laughed it off. "I think I'll go back to building buildings if it doesn't work out," he said.
Sen. Marco Rubio of Florida, seeing an opening to position himself above the spat, eventually interjected, mocking his rivals.
"I hate to interrupt this episode of Court TV," he said, drawing laughs and applause. He then sought to refocus the conversation on President Barack Obama's shortcomings and what he said was a need to revive the country, safe terrain for Republican primary voters.
Cruz, too, tried to rise above the fray by repeatedly attacking the president, decrying Obama's omission from the State of the Union speech on Tuesday any mention of the Navy sailors who were temporarily detained by Iran this week. "It was heartbreaking, but the good news is, the next commander-in-chief is standing on this stage," Cruz said.
At first, his other rivals joined in, trying to keep the focus on Obama and Hillary Clinton.
"On Tuesday night, I watched story time with Barack Obama, and it sounded like everything in the world was going amazing," said Gov. Chris Christie of New Jersey, who said that U.S. alliances were in bad need of repair and that adversaries needed to understand "the limits of our patience." He also said Cruz was right in calling Obama to account for not mentioning the face-off with Iran.
Former Gov. Jeb Bush of Florida said Obama was living in an "alternative universe" in which the Islamic State militant group was not a lethal threat to America, terrorism was being contained, and China and Russia were not on the rise. "American leadership in the world is required for peace and stability," he said.
The candidates also sought to find provocative new ways to tar Clinton.
"If she gets elected, her first 100 days, instead of setting an agenda, she might be going back and forth between the White House and the courthouse," Bush said,
drawing applause.
Rubio sought to top that. "I would go, first of all, one step further," he said. "She wouldn't just be a disaster. Hillary Clinton is disqualified from being commander-in-chief of the United States." Over applause, Rubio continued, "Someone who cannot handle intelligence information appropriately cannot be commander-in-chief, and someone who lies to the families of those four victims in Benghazi can never be president of the United States."
Rubio seized an opportunity to challenge Christie's conservative credentials on a host of issues important to party activists.
"I like Chris Christie, but we cannot afford to have a president of the United States that supports Common Core," he said about the education standards. "We cannot afford to have a president of the United States that supports gun control."
Saying Christie had also contributed to Planned Parenthood and backed Justice Sonia Sotomayor's appointment to the Supreme Court, Rubio added: "All I'm saying is our next president has to be someone that undoes the damage Barack Obama has done to this country. It cannot be someone that agrees with his agenda."
Christie responded with ridicule, recalling that Rubio had repulsed an attack from Bush at an earlier debate by suggesting that Bush had been told to criticize him out of desperation.
Though Christie ridiculed senators as all talk, no accountability, he largely avoided responding with specific critiques of Rubio's views — though he recalled that Rubio had once lauded him as a "conservative reformer that New Jersey needed."
Cruz, faced with a question about his failure to disclose a large loan in his 2012 Senate race, attacked The New York Times and called the lack of disclosure "a paperwork error."
"The entire New York Times attack is that I disclosed that loan on one filing with the United States Senate that was a public filing, but it was not on a second filing with the FEC," he said, referring to the Federal Election Commission. "Both of those filings were public."
Cruz's bank loan was the focus of a Times article published Wednesday night, which reported that he and his wife borrowed up to $1 million from Goldman Sachs and Citibank as they were financing his 2012 Senate primary race in Texas. Cruz did not disclose the loans on campaign finance reports. During that race, he railed against Wall Street bailouts and the influence of big banks in Washington, a populist, outsider message that is also central to his presidential campaign. After his 2012 victory, he said in interviews that he and his wife, Heidi, had sacrificed "all we had saved" by putting personal funds into his Senate campaign.
Looming over Thursday's debate were the Iowa caucuses, 17 days away on Feb. 1, and the New Hampshire primary on Feb. 9.
After months of jockeying for advantage on policy issues and leadership credibility, the seven Republicans in the prime-time debate are now almost entirely preoccupied with those first nominating contests, tailoring their political messages and lines of attack to the groups of voters each candidate is trying to win over, galvanize or steal from a rival. If the debates in the last five months of 2015 were preseason scrimmaging, the debates from North Charleston forward are more like late-season competition in which the results become steadily more consequential.
This new period begins with fewer candidates on the main debate stage. Sen. Rand Paul of Kentucky and Carly Fiorina were excluded on Thursday, and the Iowa and New Hampshire contests are likely to shrink the field even more. The winnowing allows more time for the top candidates to attack and counterpunch, with at least the possibility of more substance and less circus.
Many Republicans are expecting the nomination fight to narrow to just three candidates: Trump, Cruz and a representative from the so-called establishment wing of the party.
Trump and Cruz, who were unofficial allies through the summer and fall, now appear virtually tied in several Iowa polls, which has led Trump to begin applying his psychological warfare against Cruz.
Having unnerved Jeb Bush and others with his endless taunts, Trump has begun arguing that Cruz may not be eligible for the presidency because he was born in Canada. Cruz, whose discipline in sticking to his message is one of his strengths, has seemed irritated at times at having to explain again and again that his birth to an American mother clears any constitutional hurdle.
But Trump's retort — that Republicans cannot risk the distraction of a Democratic lawsuit if Cruz is the nominee — has introduced a measure of doubt that he hopes will give Iowans pause.
Cruz, after playing nice for weeks in hopes of inheriting Trump's supporters should Trump falter, started striking back this week, trying to link Trump to Clinton and questioning his command of foreign policy and his "New York values."
Rubio, for his part, is hoping to place at least third in Iowa and emerge as the Republican establishment favorite.