Top Republicans are increasingly worried that GOP candidates this fall might be burned by a fire that's roaring through the conservative base: demand for the repeal of President Barack Obama's new health care law. It's fine to criticize the health law and the way Democrats pushed it through Congress without a single GOP vote, these party leaders say. But focusing on its outright repeal carries two big risks. Repeal is politically and legally unlikely, and grass-roots activists may feel disillusioned by a failed crusade. More important, say strategists from both parties, a fiercely repeal-the-bill stance might prove far less popular in a general election than in a conservative-dominated GOP primary, especially in states such as Illinois and California.