|Florida, with its large Hispanic population, holds the key to the Republican candidates' political fortune [Reuters]
The rival Republican presidential hopefuls, Newt Gingrich and Mitt Romney, have clashed over immigration, space policy and taxes in the second debate in a week before the crucial Florida presidential primary on January 31.
Gingrich cast Romney, a former Massachusetts governor, as the most anti-immigrant candidate of the four contenders for the Republican nomination in the campaign debate in Jacksonville, Florida, on Thursday.
He responded by attacking Gingrich for "over-the-top" personal attacks.
"The idea that I'm anti-immigrant is repulsive ... it's simply the kind of over the top rhetoric that's characterised American politics too long," Romney said to audience applause in Jacksonville, Florida.
"I think you should apologise for it and recognise that having differences of opinions does not justify labelling people with highly charged epithets."
Gingrich, a former House of Representatives speaker, criticised Romney's proposal of "self-deportation" of illegal aliens, saying: "I don't think grandmothers and grandfathers will self-deport."
But Romney, who said his father was born in Mexico and his father-in-law in Wales, replied: "I'm not going to find grandmothers and deport them."
A massive 11 million illegal immigrants are said to live in the shadows in the US, and Florida, with its large Hispanic population, may change the fortune of candidates, vying to get Republican nomination to face Barack Obama in November.
When Ron Paul, a Texas congressman, was asked to comment on the issue, he said some of the measures proposed by his rivals were difficult to implement, and called for focusing on the US-Mexico border instead of on the Middle East.
Opinion polls make the race a close one, with Rick Santorum, a former Pennsylvania senator, and Paul trailing far behind.
Romney and Gingrich also clashed over their earnings from mortgage firms Fannie Mae and Freddie Mac.
Gingrich said Romney had profited from home foreclosures that have hurt Florida, and asked how much of Romney's personal fortune came from those foreclosures.
Romney defended the investments, saying it was "blind trust" that controlled his finances and that Gingrich himself owned mutual funds that also invested in the quasi-government lenders.
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Al Jazeera's Alan Fisher, reporting from Jacksonville after Thursday's debate, said: "If you ask most observers, Romney had a good night, a very good night here in Florida.
"He went on the attack very early on, he was very competitive.
"He didn't let Gingrich away with anything, including some of the wording of the ads that his campaign is running here in the state.
"He also accused Gingrich of pandering, seeing to each voter in each state exactly what they want to hear."
Santorum, who won the Iowa Republican caucuses, appealed to both Romney and Gingrich not to attack each other and instead focus on the main issues.
He said Romney is "a wealthy guy because he worked hard", and at the same time said "Gingrich's work advising companies after leaving government is not the worst thing in the world".
For his part, Gingrich reiterated his stance on Palestinians as "invented" people. To a question from a man of Palestinian descent, Gingrich said that Palestinians were, in fact, invented in the 1970s. He said before that they were simply identified as Arabs.
He said he would be a steadfast supporter of Israel.