McCain Surpasses Obama for the First Time on Intrade

Many Obama supporters during the last few weeks have been downplaying Obama's fall in the polls by pointing out that he had kept a strong lead in political prediction markets such as Intrade, see for example this Daily Kos post and this one too. A Daily Kos poll available in the latter post indicated that as of this day 77% of the participants thought Intrade was more trustworthy than daily tracking polls.

The explanation given for the phenomenon was normally a variation of (1) talk is cheap and (2) prediction markets capture long-term trends while polls are affected by short-term political factoids.

I wonder what creative argument we'll hear now that McCain is ahead of Obama in the prediction markets for the first time since both locked their nominations:

Another interpretation, represented by this irate comment on a Mankiw's post, is that prediction markets just amplify headline news and therefore mean absolutely nothing. According to the author of the post, it's all easy money up for grabs: the post suggests that Obama's chances of winning are yet around 80% (I can only wonder where this number comes from).