Thanks to some friends who turned me on to it, I've been spending far too much time on Intrade recently. What the curves show is bettor perceptions of what the voters will do (based on voter perceptions). Note that the prices will not mirror the electoral split - they are a reaction to the likelihood of a certain electoral split's ability to call the outcome in advance. This is affected by the size of the split and the days until the election. In this way, a 60-40 popular split would probably have been a 95-5 on Intrade, even a week out.
No surprise here: McCain's curve jumps when the Palin nomination starts the buzz, then begins its plummet in mid-September (when Lehman Bros. went belly-up).
This is in line with my own and I think most people's intuitions - that McCain was already fighting a strong Bush-20%-approval headwind, but the meltdown is what got him. The damn shame here is that the GOP's albatross doesn't seem to have come from the Iraq War, or the erosion of civil rights, or the distortion of the tripartite model of government created by the Founders, or the damage to our moral imperative around the world. No, it was a bad hurricane, and a financial meltdown. Neither were entirely Bush's fault.
Full disclosure: if we wanted our financial system to keep running, we needed the bailout. I support what Paulson has done; we're between the Scylla of nationalization and the Charybdis of the economy getting sucked down the drain. But most Americans seem not to have been so thrilled about the bailout - perhaps this is part of the LP's relative success this time around?