Birth of a counter-factual

What if Jim Callaghan had gone to the country in 1978? What if John Kennedy had lived? What if Tony Benn had become Deputy Leader of the Labour Party? What if John Smith had lived?

They're all fun - because endlessly debatable - and all, ultimately, pointless. And we're about to live through our very own counter-factual. What if Gordon Brown had gone to the country in Autumn 2007?

It looks less and less likely that he will - the Conservatives haven't imploded, the polls are still looking good, but not magnificent, and boundary changes and so forth make improving on his current position difficult to say the least. But, as John Rentoul says, now is arguably the most propitious time. He has the excuse of seeking a mandate - and the opposition, having called for him to do so, would be unable to exploit the 'unnecessary nature' of the election. He still has a veneer of newness, a veneer granted to all new Prime Ministers, and usually of short duration. He has a decreasing window in which existing problems can convincingly be blamed on the previous administration.

But he won't go. And so when he does, in Spring 2008 or 2009 perhaps, everything will be viewed through this little counter-factual prism. Why didn't Gordon go in Autumn 2007?