BEDFORD, N.H. — When it comes to health care, Mitt Romney is hoping to have it both ways, even as he accuses the White House of doing the same.

In the weeks since President Obama and the Democratic Congress enacted their health care overhaul, Mr. Romney, the once and presumably future candidate for the Republican presidential nomination, has confronted an issue that is alternately viewed as a strength and a vulnerability.

As he promotes himself as a problem-solving pragmatist, Mr. Romney can justifiably point to the landmark universal coverage law in Massachusetts that he, as governor, proposed in 2006. But as he appeals to conservative activists and Republican primary voters, he is trying to draw nuanced distinctions between his Massachusetts law and the federal legislation that shares many of its fundamental elements, including a requirement that people have insurance.

The core of his argument is a federalist assertion that the new law usurps powers that properly reside with the states.