The conventional wisdom is that Barack Obama is taking a hit in the polls because of health care.
You could use our most recent national poll to make that argument. 90% of McCain voters are opposed to Obama's health care plan while only 81% of his voters are in support of it.
Let's dig a little deeper though. Is Obama losing the overall support of his 2008 voters that he hasn't sold yet on health care? The answer, for the most part, is no. That group still approves of him by a margin of 64/27.
Only 2% of voters nationwide overall voted for Obama but now disapprove of him on health care and disapprove of his overall performance.
Now let's look at another group- people who voted for McCain but support what Obama's trying to do on the issue. They account for 3% of voters nationwide, and within that group 90% of them approve of Obama's overall performance.
The number of Obama voters who've abandoned him because of health care and the number of McCain voters who've joined him because of health care appears to be basically equivalent. And that's why his approval rating is pretty much identical to the share of the vote he won last November.