Donald Trump began the second Republican presidential debate with a bang, throwing barbs in all directions, but was quiet for long stretches as 10 fellow candidates for the 2016 presidential nomination discussed serious issues.
Standing at centre stage, the front-runner in the contest said he had a "phenomenal temperament" and a record in business that would help him on the world stage.
The billionaire businessman's temperament was again up for discussion during a marathon debate. Mr Trump has made a series of incendiary comments about women and Hispanic immigrants and remains a long-shot candidate for the White House.
His unexpected rise and surprising durability is seen as a reflection of voters' frustration with Washington and career politicians. He drew a heavy challenge from another Washington outsider with a business background: former Hewlett-Packard chief executive Carly Fiorina, the only woman in the Republican race.
Ms Fiorina earned praise for her debut performance in the party's main debate in Simi Valley, California, commanding the three-hour event's first half - when the television audience was likely to have been the most engaged.
Mr Trump has become increasingly critical of Ms Fiorina as her standing has risen, but she drew the night's first loud ovation when asked about his earlier denigration of her looks, which he later denied was a reference to her appearance.
"I think women all over this country heard very clearly what Mr Trump said," she told the show.
Mr Trump retorted: "She's got a beautiful face, and she's a beautiful woman."
His climb to the top of the field has unnerved Republican leaders who fear the former reality TV star is damaging the party's brand and threatening its chances of winning back the White House after President Barack Obama's eight-year tenure ends.
Mr Trump has so far been immune to criticism for his lack of specific policy proposals, his caustic rhetoric and his uneven support of conservative principles.
The clash that signified the broader battle within the party was between Mr Trump and former Florida governor Jeb Bush, the son and brother of former presidents who more than any other candidate is seen as a representative of the Republican establishment.
Mr Bush came into the debate facing questions about whether he had the grit to take on Mr Trump. In the debate's early moments, Mr Bush tried to challenge Mr Trump directly but was repeatedly interrupted.
As Mr Bush tried to finish an answer, Mr Trump chimed in: "More energy tonight, I like that" - a reference to his frequent critique that Mr Bush is a "low energy" candidate.
Mr Bush said Mr Trump should apologise for bringing his wife, a US citizen born in Mexico, into a political debate. Mr Trump has suggested Mr Bush is too soft on America's immigration crisis because of his wife.
Mr Trump refused to apologise, stood by his criticism of Mr Bush for answering some questions on the campaign trail in Spanish and called his opponent"weak on immigration".
Florida senator Marco Rubio jumped in and said it is important to speak Spanish to communicate with immigrants who might become Republican voters - highlighting a priority for a party that has overwhelmingly lost the rapidly growing Hispanic vote in recent presidential elections.
Mr Rubio reminded voters about his compelling personal story, including his parents' move to the US from Cuba. He recounted his grandfather, whose English was shaky but who idolised Ronald Reagan.
As Ms Fiorina and Mr Trump debated their business successes, they were interrupted by New Jersey governor Chris Christie, who said Americans did not care about the candidates' resumes.
"You're both successful people. Congratulations," Mr Christie said. "The middle class in this country who's getting ploughed under by Barack Obama and Hillary Clinton, let's start talking about those issues tonight and stop this childish back-and-forth between the two of you."
Rand Paul, the only candidate to directly challenge Mr Trump in the first debate, said he worried about his opponent as commander-in-chief. He cited Mr Trump's "careless language" and attacks on people's appearance.
Mr Rubio and Wisconsin governor Scott Walker, who had been seen as early favourites but lost ground as Mr Trump surged, managed to offer detailed policy proposals and criticisms in limited air time.
Softly spoken retired neurosurgeon Ben Carson entered the debate with high expectations after a recent rise in the polls that determine debate participation. But he largely faded to the background on the crowded debate stage. In a rare standout moment, the political novice said he does not "lick the boots of billionaires".
Other candidates included Ohio governor John Kasich, former Arkansas governor Mike Huckabee, and conservative senator Ted Cruz.