Sean Trende's article, Can Obama Resist the Forces of  Gravity?, on RCP is worth the read.  He succinctly explains the Obama campaign strategy.  Expect O's campaign to launch a new low-ball, vicious, gutter "surprise" attack on the eve of the VP debate or by Biden himself during the debate.  But this time, the voters aren't buying the bullsh** they're selling.  If Trende is right, and I think he is, once Romney takes even the slightest of  leads in the polls, Obama is finished.