MANCHESTER – Hillary Rodham Clinton's backup plan if she falters in Iowa can be summed up in two words: New Hampshire.

Clinton's Democratic team is preparing television ads here criticizing Barack Obama's health care plan and working to build what campaigns call a firewall. If the Obama presidential campaign ignites in Iowa, she wants to be ready to cool him off in a state where her organization is strong and her support has proven durable.

This past weekend, the Clinton campaign already had volunteers going door-to-door with fliers criticizing Obama on health care, and possible TV ads against him were screened for focus groups.

Advisers to the New York senator acknowledge there's been uneasiness as Obama has risen in national and several early state polls, including Iowa and New Hampshire. But they insist their master blueprint - emphasizing Clinton's experience, toughness and ability to withstand Republican attacks - remains sound.

►CNN/WMUR poll: Hillary's NH lead all but gone; Huckabee still far behind
►Suffolk/WHDH poll: Clinton's NH lead shrinks; McCain moves into second place
►Politico.com: Clinton is no longer a sure winner in NH
►Washington Post: Bill Shaheen says Obama's drug use is a political liability

"This is ultimately going to come down to two questions for undecided voters: Which is the Democrat best positioned to win in November, and which one is best qualified to start from the very first day give the country a fresh start," said Tom Vilsack, a former Iowa Democratic governor who serves as national co-chair of Clinton's campaign.

Still, with the former first lady locked in a tight three-way contest in Iowa with Illinois Sen. Obama and former North Carolina Sen. John Edwards, her campaign is working on two tracks: reinforcing her support there while creating a "Plan B" should she come up short in the state's Jan. 3 leadoff caucuses.

Clinton advisers believe she can survive a loss there to Edwards, who is running well in Iowa but has smaller campaign organizations in the other early-voting states.

Edwards' campaign, meanwhile, hopes for a repeat of the Howard Dean-Dick Gephardt scuffle in Iowa that resulted in John Kerry's nomination four years ago. The former North Carolina senator is hanging back and hoping Clinton and Obama destroy each other.

Placing second in Iowa to the well-funded, well-organized Obama, the Clinton people acknowledge, could be a much more severe blow.

That's why New Hampshire, which crowned Bill Clinton the "comeback kid" when he first ran for the Democratic nomination in 1992, has emerged as a prime target for his wife this time. The state holds its primary Jan. 8, just five days after the Iowa contest.

"The only thing you can do to insulate yourself is to make sure your organization is airtight and to make sure the people who are with you are with you through the end," said Clinton's New Hampshire director, Nick Clemons.

To that end, the Clinton campaign ordered focus groups in New Hampshire last weekend to test television ads against Obama on his health care plan, which does not mandate universal coverage as Clinton's does. Her New Hampshire volunteers have begun going door to door with literature arguing his plan could leave as many as 15 million people uninsured.

Asked yesterday about the Clinton campaign's literature, Obama said he hadn't seen it but believed it was "entirely legitimate" to compare candidates' positions on health care and other matters.

Hinting at Clinton divisiveness, Obama said of overhauling health care, "The issue really is how are we going to get it done, because there are all kinds of 10-point plans out there that are gathering dust on the shelf because no one was able to actually pull the country together to deliver."

Voters in Iowa received a similar Clinton direct mail piece this week, signed by Vilsack. He and other Clinton strategists reject the notion that such an effort is negative.

"It's an important distinction, not negative at all. Iowans want everyone covered," Vilsack said in an interview.

Indeed, Clinton has toned down her sharp criticism of Obama, just days after raising questions about his character and accusing him of peddling "false hope." Her advisers say she had needed to set the record straight after absorbing months of criticism from her rivals, but they have since concluded her barrage didn't work.

Even so, Clinton's tongue-lashing of Obama laid the groundwork for a story line her advisers believe will serve her well over time: that little is known about the young Illinois senator, and that his record bears considerably more scrutiny and vetting.

For her part, Clinton has a very different challenge: winning over voters who believe they know her too well.

With her long record in public life, her advisers are searching for ways to cast her as an agent of change in a political environment where voters - especially Democrats - say they are eager for a new direction. The campaign has sought to reframe the issue, painting Obama as someone who talks about change while Clinton actually makes it happen.

"You'll see us continue to sharpen the message and illustrate that this is a very serious election," Clinton's lead strategist Mark Penn said. "The voters have a choice about who would make the best president, and every time it comes down to that choice, she comes out on top."