Republican presidential candidate former Massachusetts Governor Mitt Romney makes a point during the Republican presidential candidates debate in Jacksonville, Florida January 26, 2012. [Photo/Agencies]

WASHINGTON - Republican presidential candidates Mitt Romney and Newt Gingrich exchanged fires Thursday night in the final debate before the Florida primary.

The former Massachusetts governor and the former House speaker clashed with each other on the issue of illegal immigration immediately after the debate, which also pitted Texas congressman Ron Paul and former Pennsylvania Senator Rick Santorum, kicked off on the campus of the University of North Florida.

Commenting on Romney's recent remarks that illegal immigrants could be pressured into practicing "self-deportation," Gingrich said he thinks the idea is unworkable when it comes to older illegal immigrants who have been here for a long time.

Romney touted the idea of "self-deportation" in Monday night's debate, arguing that illegal immigration can be curbed by denying public benefits to them.

The former governor also called Gingrich's allegations that he is anti-immigrant "inexcusable."

"The idea that I'm anti-immigrant is repulsive," he said. "It's simply the kind of over-the-top rhetoric that's characterized American politics too long."

Illegal immigration is a hot issue in Florida, where people of Hispanic origin make up 22.5 percent of the state's population, compared with 16.3 percent of the U.S. population, according to census data from 2010.

The voting bloc is critical for a candidate not only in the primaries but also in general elections.

During the debate, Romney and Gingrich also attacked each other over their respective connections to Fannie Mae and Freddie Mac, the two mortgage giants blamed to be responsible for the collapse of the housing market.

This is particularly an issue in Florida, which has one of the highest foreclosure rates in the nation.

"Speaker Gingrich was hired by Freddie Mac to promote them, to influence other people throughout Washington," Romney said.

In response, Gingrich said Romney was covering up his own investments in the two mortgage giants. "We discovered to our shock that Governor Romney owns shares of Fannie Mae and Freddie Mac," he said.

Florida is seen as a pivotal battleground after Gingrich claimed victory in South Carolina, effectively ending Romney's hope of locking up the nomination by the end of this month.

Romney needs to win in the Sunshine State to prove that he is still the most electable candidate, while Gingrich needs a victory there to demonstrate his viability.

The latest CNN survey suggested that the two candidates are in a dead heat in the state, which holds its primary on January 31.

Thirty-six percent of likely Republican voters in Florida would back Romney while 34 percent would choose Gingrich, according to the poll released Wednesday.

Santorum and Paul trailed with 11 percent and 9 percent respectively.