It's health care, stupid.

With a House vote on expanding S-Chip set for this afternoon, a new poll out from the Dem firm Democracy Corps (no link yet) concludes that the battle over the children's health care program is shaping up as a very costly one for Republicans, one that could very well resonate in 2008 as voter concerns about health care soar:

Health care can emerge as the central economic battle of the 2008 election cycle. That is reflected in more and more people choosing health care as the top problem overall making it the top domestic concern. Voters concerns with health care remain primarily in the rising costs as well as in being sure they will always have access to quality care.

The battle over children’s health care, S-CHIP, has the chance to crystallize this issue to the great disadvantage of President Bush and the Republicans. Voters reject the President’s veto threat by almost two-to-one, preferring the expansion of insurance.

The poll finds that voters side with Dems on the issue by 60%-35%; that independents want the program expanded by a 34-point margin, 62%-28%; and that voters in Republican-held districts also overwhelmingly favor the expansion, 55%-39%.

Fueling these numbers, the poll finds, is an explosion in voter concern about the health care issue in general. In another ominous 2008 sign for the GOP, the survey says that the percentage of voters who see rising health care costs as a "very serious problem" has increased an astonishing 12 points in only the last two years. We'll bring you the full poll when it's on line.

Late Update: The full poll is here.