Nate Silver explains:
The theory seems to rest on the notion that Mr. Obama could use the health care bill to rally his base, either by railing against the Supreme Court or by trying to advance a new plan.
There are a few basic problems with it:
1. Mr. Obama does not face a major problem with his base, but his standing is tenuous with swing voters.
2. Among swing voters, the health care bill is not very popular.
3. The Supreme Court declaring the health care bill unconstitutional will not make it more popular among swing voters.