Could Cameron have survived an autumn election?

I was on BBC Radio Four’s Talking Politics today with Anne McElvoy of the Standard and Michael White of the Guardian – and Dennis Sewell in the chair. During it I made a point which I had thought uncontroversial: how close Cameron came to political destruction last autumn.
 
My theory is that if Brown had called that election, he’d have won. Cameron bluffed beautifully at Blackpool: his Etonian fearlessness saved him and his party. But his bold new policies would not have withstood the scrutiny of an election campaign (especially the back-of-the-envelope figures about non doms). A defeated Cameron would have had to quit, and the topic of discussion now would be a Tory leadership election.
 
Anyway, Michael said he strongly disagreed – which surprised me. Did he think Cameron would have won in November or that he wouldn’t have quit if he’d lost? We didn’t get a chance to explore it.