WASHINGTON - Rick Perry is "a career politician." Mitt Romney has been campaigning full time for nearly five years. Those barbs were shot back and forth ahead of a debate in the key battleground state of Florida, as presidential candidates sharpen their rhetoric for fellow Republicans more than their once-favourite target, President Barack Obama.

Five months remain until the first nominating contests, leaving little time for some of the candidates trying to break free of the pack. Their camps descended on this week on Florida, a swing state rich with elderly residents who tend to vote in large numbers.

A poll released early Thursday indicates Florida Republicans slightly prefer Perry, the front-runner, over Romney in their party's battle to find a nominee to face Obama next year.

Perry was favoured by 28 per cent of the 374 registered Republican voters, compared with 22 per cent who want Romney as their nominee. The random telephone survey, conducted Sept. 14-19 by Quinnipiac University, has a margin of error of plus or minus 5.1 percentage points.

Republicans aren't holding back their attacks on Perry, the Texas governor.

For instance: Texas added jobs during the economic recession under Perry's leadership. But unemployment went up last month and is at the highest level since 1987, rival Mitt Romney noted.

Texas added jobs during the economic recession under Gov. Rick Perry's leadership, he notes. But unemployment went up last month and is at the highest level since 1987, rival Mitt Romney says.

Romney filled in Massachusetts' $3 billion budget hole without raising taxes as governor. Yet the state trailed 46 others in job creation, Perry shot back.

Perry's campaign didn't address Romney's questions and instead Ray Sullivan, its chief spokesman, swiped at a rival who "seems to forget he's a Republican."

Romney has spent years building an organization and has aggressively worked to raise money. Perry, who entered the campaign just last month, quickly jumped to the lead in national polls as Republicans looked for an alternative to Romney.

During their last debate, the two directly confronted each other on their records and the questions become more pointed in the days since.

With Romney and Perry elbowing each other for front-runner status -- and conservative, anti-tax tea party darling Michele Bachmann trying to wedge herself into the top tier -- the presidential contenders scheduled a forum on their faith and a head-to-head debate for Thursday.

They will also make appearances at a conservative conference on Friday and some will visit a nonbinding test vote of the party faithful on Saturday.

An independent pro-Bachmann group was ready to start airing advertisements aimed at Perry in the crucial nominating state of Iowa. "The question is about Rick Perry's character," the Keep Conservatives United ad states in the 30-second commercial to air on Fox News Channel in Iowa.

The ad follows Bachmann's criticism of Perry's record in Texas and echoes conservatives' criticism of vaccines he mandated.

And Rep. Ron Paul of Texas, a favourite of the party's libertarian wing, renewed his criticism of Perry as a typical politician.

"He knows what people are thinking about, that's how politicians operate," Paul told reporters on Wednesday before heading to Florida.

Also set to join that debate: Georgia businessman Herman Cain, former House of Representatives Speaker Newt Gingrich, former ambassador to China and Utah Gov. Jon Huntsman and former New Mexico Gov. Gary Johnson.