Speaking before a crowd of conservative activists in New Hampshire Friday, former Massachusetts Gov. Mitt Romney again faced questions about the healthcare plan he championed as Bay State governor.

Romney called the Massachusetts law "an experiment," admitting that "some parts didn't work," but he didn't directly answer a question on whether or not he regretted signing it into law.

"I went to work to try to solve a problem," Romney said of the Massachusetts law, which has drawn comparisons to the law championed by President Obama. "It may not be perfect -- by the way, it is not perfect -- some parts of that experiment worked, some parts didn't, some things I'd change."

Some conservative critics have dubbed the law "RomneyCare," noting its inclusion of a mandate requiring people to purchase health insurance.
Romney, meanwhile, blasted the federal healthcare law as "unconstitutional," warning, "it will bankrupt us."  

"You will note that [Obama] and the Democrats constantly want to give me credit for their plan," Romney said, alluding to recent comments from Obama and national Democrats likening the two plans. "You know there's a method to their madness. But let me tell you this, if and when I have the occasion to debate President Obama, I'm gonna ask him this question: 'Mr. President, why didn't you call me and ask how it worked?'"

Romney was one of five rumored presidential hopefuls who took the stage Friday at a forum hosted by Americans for Prosperity. He was joined by former Minnesota Gov. Tim Pawlenty, former Sen. Rick Santorum (Pa.), Rep. Michele Bachmann (Minn.) and talk radio host Herman Cain.

All five blasted President Obama's economic policies and called for repeal of the healthcare law.

For Romney, it marked his first major appearance in an early presidential state since officially forming an exploratory committee earlier this month, but his speech wasn't free of missteps.  

Alluding to the "misery index" that Ronald Reagan hit President Carter with during the 1980 presidential race, Romney said of the president, "We're gonna have to hang the Obama misery index around his neck." 

Continuing his line of economic attack on Obama, Romney almost talked himself into trouble, but he stopped himself mid-sentence after uttering, "we're gonna hang him with that."

Here's Romney's full quote: 

We're gonna have to hang the Obama misery index around his neck, and I'll tell you the fact that you've got people in this country really squeezed with gasoline getting so expensive, with commodities getting so expensive; families are having a hard time making ends meet. So we're gonna have to talk about that. And housing foreclosures and bankruptcies and higher taxation -- we're gonna hang him with that -- so to speak, metaphorically with -- you have to be careful these days. I've learned that.