Updated

BARTLETT, N.H. -- Call it an attempt to address an obvious political vulnerability.

Republican presidential hopeful Mitt Romney on Saturday derided President Barack Obama's health care law -- modeled in some ways after one the ex-governor signed in Massachusetts -- as a misguided and egregious effort to seize more power for Washington.

"Obamacare is bad law, bad policy, and it is bad for America's families," Romney declared. "And that's the reason why President Obama will be a one-term president." He vowed to repeal it if he were ever in a position to do so, and drew hearty cheers from his Republican Party audience.

Then, raising the Massachusetts law, Romney argued that the solution for the unique problems of one state isn't the right prescription for the nation as a whole, and he acknowledged: "Our experiment wasn't perfect -- some things worked, some didn't, and some things I'd change."

"One thing I would never do is to usurp the constitutional power of states with a one-size-fits-all federal takeover," Romney said, again earning applause. "The federal government isn't the answer for running health care any more than it's the answer for running Amtrak or the post office."

With that, he used his first appearance before New Hampshire Republicans since the midterm elections to start addressing head-on the issue that's certain to be a hurdle in his all-but-certain presidential campaign.

Romney's states-rights pitch is one that GOP primary voters are likely to hear over the next year as he tries to persuade them to overlook his flaws because he alone is the strongest Republican to challenge Obama on the country's top issue -- the economy.

The failed candidate of 2008 is expected to formally announce a second candidacy later this spring. Campaign signs posted along the road leading to the hotel where he was speaking may have gotten a bit ahead of him. They said "Mitt Romney for President" and suggested that the theme would be "True Strength for America's Future."

Romney and his aides insisted they were old signs.

Among Romney's biggest challenges: explaining to GOP primary voters why he signed a law that became the foundation for Obama's national overhaul. Passed by Congress last year, Obama's health care law has enraged conservatives who view it as a costly government expansion and intrusion into their lives because it mandates insurance for most Americans.

Romney all but ignored the topic in his last major public appearance last month at the Conservative Political Action Conference in Washington.

But, since then, the similarities with Romney's 2006 law in Massachusetts have increasingly been dogging him. The state's universal coverage law has a more sweeping mandate for people to get insurance than exists in Obama's law -- and penalizes the uninsured more severely.

Obama praised the efforts in Massachusetts during a meeting with governors at the White House, saying: "I agree with Mitt Romney, who recently said he's proud of what he accomplished on health care by giving states the power to determine their own health care solutions. He's right."

Also, Massachusetts Gov. Deval Patrick, an Obama friend, said Romney deserves a lot of credit on health care. "One of the best things he did was to be the co-author of our health care reform, which has been a model for national health care reform," he said.

The praise from Democrats provides fodder for Romney's Republican primary opponents; some are already heaping on the criticism.

Former Arkansas Gov. Mike Huckabee says in his new book: "If our goal in health care reform is better care at lower cost, then we should take a lesson from RomneyCare, which shows that socialized medicine does not work." It was a play on the word that conservative critics use to describe the national law: Obamacare.

Mississippi Gov. Haley Barbour, who is likely to run for president against Romney, took a shot at Romney when he testified before a House committee reviewing Obama's health care overhaul. He lumped Romney in with a late liberal icon and an Obama friend in saying: "Senator (Edward M.) Kennedy and Governor Romney and then Governor Patrick, if that's what Massachusetts wants, we're happy for them. We don't want that. That's not good for us."

A GOP rising star, House Budget Chairman Paul Ryan, R-Wis., also weighed in, saying of Romney's law: "It's not that dissimilar to Obamacare. And you probably know I'm not a big fan of Obamacare."

All that was the backdrop as Romney took the stage at the Carroll County Lincoln Day Dinner at the Attitash Grand Summit Hotel in northern New Hampshire.

First, he poked fun at the criticism that seems to be coming from all sides, saying "you may have noticed that the president and his people spend more time talking about me and Massachusetts health care than Entertainment Tonight spends talking about Charlie Sheen."

Then he turned serious and provided an explanation, emphasizing states' rights to a crowd from the "Live Free Or Die" state.

His coming candidacy may hinge on whether they buy it.