Republican and Democratic frontrunners descended on New Hampshire Friday as they attempted to firm up support for their White House bids in the early-voting Granite State.

Rudy Giuliani kicked off his visit to the state with a jab at New York Sen. Hillary Clinton, comparing her to 2004 presidential candidate John Kerry.

"Her positions change more frequently than anybody I have ever seen in politics," the Republican frontrunner said at a restaurant in Errol, N.H. "I remember last time John Kerry used to be accused of being a flip-flopper. She makes him look like an amateur."

The comments came after Clinton filed her candidacy papers to run in the New Hampshire Democratic primary. After filing she stood outside the State House to entreat voters for their help over the next two months.

"I know how hard this job is going to be. We're all talking about change and the American people desperately want change," she told supporters. "The failed policies of George Bush and Dick Cheney have alienated our friends, emboldened our enemies and put extra burdens on hard-working middle class Americans, so we have a lot of work to do."

Clinton stayed focused on Bush as she tries to regain her footing on the campaign trail after taking a beating from six of her Democratic opponents during a debate Tuesday in Philadelphia, especially for giving a confusing position on a New York state plan to give illegal immigrants driver's licenses. Her campaign has since blasted her opponents' strategies as the "politics of pile-on," and clarified that the New York senator supports the driver's license plan.

Clinton on Friday joked that "I don't think they're piling on because I'm a woman. I think they're piling on because I'm winning."

Democratic opponent John Edwards released a new video criticizing Clinton for the "politics of parsing," but it was Clinton who earned the endorsement Friday of New Hampshire State Sen. Lou D'Allesandro, a former Edwards backer.

Not to be outdone, Giuliani accepted the endorsements of Missouri Sen. Kit Bond and Minnesota Sen. Norm Coleman Friday morning in Washington before heading to New Hampshire to campaign. And he took more direct swipes at Clinton, opting to give Democratic candidate Barack Obama a pass when asked his thoughts on Obama's claims that he would negotiate with Iran unconditionally.

"I can feel comfortable telling you what Sen. Obama's position is and I respect a man for taking a position. In Hillary's case, I have to be a little bit more careful because it may not be the same position today as it was yesterday," he said.

Bond invoked 9/11 when describing the former New York City mayor during his endorsement.

"We need to make America's mayor America's president ... The whole world marveled at what he was able to do," Bond said of Giuliani's response to the terrorist attack while he was mayor. Bond will be the national co-chairman of Giuliani's campaign.

Bond, who serves as the ranking member of the Senate Intelligence Committee, and Coleman bring the total number of senators endorsing Giuliani to three, trailing rivals Mitt Romney and John McCain in Senate endorsements. Sen. David Vitter of Louisiana endorsed Giuliani months ago.

The two endorsements could boost the former New York City mayor's presidential bid in key states. Minnesota is a traditional swing state, and is the place where the Republican National Convention is being held in early September 2008.

But Friday was supposed to be all about New Hampshire for Giuliani, who also visited Dixville Notch, which since 1952 has been where voters cast the first ballots.

A poll taken of 600 likely New Hampshire voters between Oct. 26 and 29 by the American Research Group showed Giuliani with 23 percent support and Romney with 30 percent.

But that's a slight gain for Giuliani, and the candidate may see an opening in New Hampshire to overtake Romney, who is already well-known in New England for serving as governor of Massachusetts. Still, Romney just put out a new television ad in New Hampshire accusing Clinton of inexperience, while Giuliani has yet to launch any ads in the state.

Giuliani's visit also came as questions were being raised about his latest radio ad.

The Concord Monitor reported Friday that a state health care advocacy group has asked the candidate to pull the ad, where he talks about his battle with prostate cancer. In the ad, he says his chance of surviving is 82 percent in the United States, but only 44 percent under socialized medicine in England. New Hampshire for Health Care called on Giuliani to pull the ad, claiming the statistics were inaccurate.

Giuliani has defended his statistics.

FOX News' Serafin Gomez, Aaron Bruns, Carl Cameron and Mosheh Oinounou contributed to this report.