DES MOINES — Michael Huckabee may not want the label of Iowa front-runner heading into the final Republican debate before the caucuses, but his campaign is acting like it.

Now under constant attack from his rivals following his rapid ascent in the polls, Mr. Huckabee is likely to throw few if any jabs of his own when the GOP hopefuls meet this afternoon in Johnston, Iowa.

“We want to focus on our own message,” his campaign manager, Chip Saltsman, said in an interview yesterday.

Polls taken in Iowa this month show the former Arkansas governor with a double-digit over Mitt Romney, prompting Mr. Romney to release what is seen as the first negative television ad of the campaign this week.

The spot explicitly highlights Mr. Huckabee’s support for giving in-state tuition breaks to illegal immigrants, an issue over which the two candidates have sparred in recent weeks.

Mr. Romney had comfortably led surveys in Iowa for months before Mr. Huckabee overtook him.

While Mr. Huckabee has welcomed the attacks from Mr. Romney and from another GOP opponent, Fred Thompson, his campaign is not relishing its status as Iowa front-runner, and the expectations that come with it. “I’m not ready to concede that,” Mr. Saltsman said.

He pointed to Mr. Romney’s sizable cash advantage and said that even with improved fund raising as a result of his rise, Mr. Huckabee would still be outspent in every area heading into the caucuses. “He’s going to blanket the state like the snow and ice did,” he said of Mr. Romney.

Mr. Saltsman was referring to the ice storm that shut down much of Iowa yesterday, forcing Mr. Huckabee and other candidates to cancel campaign events across the state. Mr. Huckabee scrapped appearances in five different cities but was able to announce the endorsement of a key foe of illegal immigration, James Gilchrist.

Mr. Gilchrist is the founder of the Minutemen Project, which has gained nationwide attention for its efforts to prevent illegal immigrants from crossing over the border from Mexico.

The endorsement from a prominent immigration hard-liner should help Mr. Huckabee rebut the charges from Mr. Romney that his support of tuition breaks as governor renders him soft on the issue.

Mr. Gilchrist praised Mr. Huckabee’s recently announced plan to secure the borders, which includes building a fence and which would force the estimated 12 million illegal immigrants currently in America to return to their home countries before applying for legal status.

The Minutemen Project has spawned heated debate on both sides of the issue, with critics likening its participants to vigilantes.

The endorsement may help Mr. Huckabee with the GOP base, but it could undermine his bid to present himself as a sunny conservative who rejects harsh rhetoric and divisiveness.

That image is central to his broader appeal, particularly in a general election should he win the nomination.

As Mr. Huckabee faces criticism from opponents and a spate of news stories unearthing questionable statements on homosexuality and AIDS, today’s debate could be a key test of his staying power in the Republican race.

Three weeks before the vote and heading into the holidays, the debate may also be one of the last chances for Mayor Giuliani, Mr. Thompson, or Senator McCain to stand out in an Iowa race that has recently been dominated by Messrs. Huckabee and Romney.

They are well behind in most polls, and Messrs. Giuliani and McCain have been looking to New Hampshire as a better opportunity for a first primary win. The Des Moines Register and Iowa public television is sponsoring the debate and will also sponsor a Democratic presidential debate in Johnson County tomorrow.