The Supreme Court's decision to uphold the Democrats' Affordable Care Act has saved the Romney campaign from its recent message muddle. Romney ran into turbulence as soon as the U.S. Department of Homeland Security issued an order on prosecutorial discretion that shields most young illegal immigrants from deportation.

The Republican candidate refused to say whether he would repeal the executive action as president. Then the Supreme Court issued its Arizona immigration decision, largely supporting the Obama administration while striking down most of the Arizona law. In the primaries, Romney had called the Arizona law a "model" for the nation.

Now that he's looking to win Hispanic support -- or at least deflate Hispanic support for Obama -- Romney is unwilling to repeat that endorsement. But he must also be mindful of alienating the anti-immigrant supporters he motivated in the primary. As the pro-immigration group America's Voice put it, Romney is "caught between a nativist rock and a demographic hard place."

The Supreme Court gives Romney a needed respite. He can stop dodging questions about Hispanics and commence attacking the president's health-care law. With right-wing commentators already in full "death of liberty" mode, contributions will be pouring into Republican campaign coffers. According to Politico, the Koch-financed Americans for Prosperity just committed $9 million for swing-state advertisements attacking the law.

This is all good news for Romney. The question is whether it will still be good news a month from now or, more importantly, in November. Romney's challenge is to attack "ObamaCare" without actually engaging substantively on the state of U.S. health care. After having produced an ambitious health reform as Governor of Massachusetts -- and we know what that led to -- as a presidential candidate Romney has offered little more than a few retread policy ideas of little consequence to tens of millions of uninsured Americans.

The danger is that the more the campaigns debate health care, the less the nation's economic doldrums will be the centerpiece of the election. Another danger for Romney is that voters will be exposed to the health care arguments anew -- and this time they might catch. While public opinions about the law are powerful, actual public knowledge is weak. A Kaiser Family Foundation poll found that 22 percent of Americans believed the health-care law had been repealed and another 26 percent were unsure. When pollsters quiz respondents about individual provisions of the law, even Republican voters respond positively to most. Partisan loyalty will surely keep Republican voters from catching the health reform bug, but independent voters could prove susceptible.

Republicans successfully campaigned against the health-care law in 2010. The question is whether a repetition of that success is possible given the expanded electorate and the extensive media coverage that accompany a presidential campaign.

There is a reason Republicans traditionally have avoided campaigning on health care. If Romney bucks that trend in the months ahead, he risks rediscovering why.

(Francis Wilkinson is a member of the Bloomberg View editorial board. Follow him on Twitter.)