If Paul wins the primaries, Obama wins the White House.
Here are the cards:
Racism - Paul is still considered the figurehead of the Tea Party. The Tea Party has been demonized as racist. If I was Obama, I'd definitely have Axelrod working on that angle for 2012. All he needs to do is divide the right, not conquer them.
Old folks - They vote. And they're scared. More people than ever are relying on the big entitlements (Medicare, social security, etc.). Imagine Paul being branded as the guy who's gonna make sure the old folks don't get their checks. Doesn't matter if it's true. All that matters is whether Axelrod can orchestrate it.
Jobs/Economy - Two big issues. People are scared because the unemployment rate is still high, and the "recovery" (lol) has faltered. But Obama is far more likely to juice the numbers (more facade, no substance) than Paul, who knows his economics. Once the debt ceiling is raised - and it will be raised - Obama will pour more money into getting those numbers in line leading up to the 2012 contest. Again, all he needs is the facade. Meanwhile, Paul is gonna be branded as the guy who's keeping good Americans out of jobs.
Axelrod can probably take Paul apart in his sleep. He's been working on this stuff ever since leaving Obama's side.
If Paul wins the primaries, Obama wins the White House. I'm thinking Obama is not even worried about the first part.