It would be a website aggregator of opinions by people known to generally be on one side of a political question where they favor the opposite side's view for a particular issue. There could be a left wing defection site and a right wing one, and maybe different ones for different countries.
Maybe it's just me, but I think those defecting viewpoints would be some of the most interesting, like the conservatives who can't stand Palin.
I'm not prominent enough to be one of the contributors, but I'd defect and agree with conservatives that Gwen Ifill has a conflict of interest. (The perceived bias could even work the other way, but it's still a problem.) (UPDATE: somewhat less of a problem now - she's just writing a chapter in the book, and hasn't written it yet.)
Meanwhile, my vice-presidential debate prediction: Palin will answer every question with one somewhat coherent, responsive sentence that any middle-schooler could've come up with after some research, followed by a bridging sentence, and then broad platitudes with an occasional memorized zinger. Biden will have a gaffe-free but toned-down performance that ignores Palin and occasionally attacks McCain. Palin will be viewed as having done exceptionally well and their ticket will get a 1 or 2 point bounce in the polls that will fade away after a week.
UPDATE 2: So the debaters performed much like I expected, but the public didn't. They read through Palin's generalities and all three polls I saw gave the win to Biden. Credit where due (to the public, I mean). (Also, everyone says to be skeptical of snap polls - why? As a measure of public opinion, I don't know why they're worse than any other poll.)
UPDATE 3: Ifill responds in a videocast here - the whole book is hers, but she hasn't written the Obama chapter yet, so she doesn't have to screw up the McCain campaign to support some predictions. To the extent it's about intergenerational change in African-American leadership, it almost doesn't matter if Obama wins or loses. Still, it's a little bit iffy.