Republican presidential hopefuls are intensifying their attacks on frontrunner Mitt Romney, hoping to his slow his drive to the Republican nomination ahead of the first U.S. primary election.

Romney is heavily favored to win Tuesday's primary in New Hampshire. But his opponents have not given up on trying to dissuade voters from choosing the former Massachusetts governor.

Much of the criticism has centered around Romney's previous career running a private investment firm where he made millions of dollars.

Social conservative Rick Santorum lost to Romney by only eight votes last week in the Iowa caucuses. While on the campaign trail in New Hampshire, he tried to discredit Romney's business experience as meaningful to the presidency.

“Business experience doesn't necessarily match up with being the commander-in-chief of this country.”

Many people say Romney's firm laid off hundreds of employees from companies it bought, while making large profits for the investors.

On NBC's “Today” show early Monday, former House speaker Newt Gingrich called on Romney to explain in more detail the impact his company had on jobs, saying he “owes us a report on his stewardship.”

Much of the political debate leading up to the New Hampshire primary has been focused on the need to create jobs to reduce unemployment.

Despite efforts of the five of the contenders to curb Romney's lead, analysts say it might be too late. Director of Boston's Suffolk University Political Research Center, David Paleologeologos, says Romney may be dropping in the polls, but it's unlikely that his losses will result in gains for any one candidate.

“Disproportionately momentum is going to Huntsman, although Mitt Romney has dropped 10 points in the last five days, and yet he is not losing very much in terms of losing ground. It is almost as if every four points that he drops, he's evenly distributing to the other candidates so that the net effect is a minus one, and so he's quietly dropped 10 points and yet he will still probably win in a landslide.”

All the candidates have been seeking to highlight their conservative credentials against the more liberal President Barack Obama, a Democrat.

The six major candidates for the Republican presidential nomination gathered over the weekend in New Hampshire for debates that focused heavily on the need to create jobs.

With Romney favored to win in New Hampshire, much of the attention has turned to who will be the runner-up. Texas Congressman Ron Paul and former senator Santorum are seen as battling for second place.

Two other major contenders for the Republican nomination are Texas Governor Rick Perry and the former U.S. ambassador to China Jon Huntsman. Neither of them is seen as likely to win a significant number of votes in the New Hampshire poll.

Many political analysts think the primary election in South Carolina next week will reveal whether the moderate Romney can rally the support of conservative voters.

New poll numbers released Monday show Romney with a 12-point lead in Florida, the next primary after South Carolina. But the Quinnipiac University poll also shows that more than 50 percent of Republican voters say they might change their minds and choose a candidate perceived as more conservative.