What if David Cameron loses his seat?

OK, it's an unlikely scenario. But his local paper is running an online poll which shows a good deal of support for the Lib Dems. And yes, I know all the caveats about online polls, and don't see this as a likely turn of events. But the possibility is there. What would be the effect if this were to actually happen? If the Tories were to be leaderless in the house?

This election is just throwing up so many surprises. It are can be May 7th now, pls? And then at least we'll all know where we stand. Hopefully in a country whose map looks like someone poured a tin of custard over it...