Donald Trump has come under attack from all sides in a fiery debate between the top Republican presidential candidates in the 2016 election.
The party's frontrunner, a billionaire businessman with no political experience, refused to apologise over comments about the wife of Jeb Bush.
And he was on the receiving end when Carly Fiorina drew huge applause, facing up to his recent jibe over her looks.
Fifteen Republicans are vying to be the party's White House nominee in 2016.
With more than a year until polling day, the second Republican debate in the Ronald Reagan Presidential Library in California saw Mr Bush and Mr Trump trading blows several times.
Their most notable clash in the debate, hosted by CNN, came when the former Florida governor demanded that the tycoon apologise to his wife for saying he was weak on immigration because she is Mexican. Mr Trump refused.
But the loudest audience response of the night came when Ms Fiorina was asked about an interview in which Trump said she could not be president because "Look at that face".
She replied, to thunderous applause: "I think women all over this country heard very clearly what Mr Trump said."
But if Mr Trump predictably took plenty of punches, as the candidate who has held a commanding lead for much of the campaign, he gave as good he got throughout the debate in his trademark style.
He returned fire on Kentucky Senator Rand Paul with an oblique personal insult about his appearance, mocked the fiscal record of Wisconsin Governor Scott Walker and introduced himself with the words: "I say, not in a braggadocious way, I've made billions and billions of dollars."
Other highlights in the debate:
- Mr Bush said the UK's former prime minister, Margaret Thatcher, should have her face on the $10 bill
- Ms Fiorina said women's health organisation Planned Parenthood should be denied all state funding, even if it triggers a government shutdown
- the only woman in the field also attacked the record of the Democratic frontrunner Hillary Clinton
- Chris Christie said Mrs Clinton should be prosecuted for using a private email server
- Marco Rubio and Mr Bush defended speaking Spanish on the campaign trail, after criticism from Mr Trump
- Mr Bush admitted smoking pot in his youth, while Rand Paul took flak for defending legal marijuana
- the Kentucky senator also said he would not send US troops back to Iraq to fight Islamic State militants
- Ben Carson, second in the polls, had a quiet night
- Ted Cruz said he was the only candidate not backing amnesty for illegal immigrants
A second-tier debate for the four other Republican candidates happened on the same stage earlier.
In a combative atmosphere, the four were split over the case of Kim Davis, a Kentucky clerk jailed for refusing to issue marriage licences to gay couples due to her Christian faith.
The Democratic Party will hold its first debate in Nevada in October, also hosted by CNN.
Iowa will be the first state to choose its candidate from each party on 1 February, and is seen as a key indicator for the race ahead. Other states hold primaries in the following weeks and months.
By next summer, each party will have a presidential nominee who will do battle in the race for the White House.
Votes will finally be cast in November 2016.