David Cameron won't debate Alex Salmond because televised debates are for losers.

The standard assumption about political debates is that the campaign with most to gain in all in favour of them while the candidate presumed to be the front-runner wants nothing to do with them. Franklin Roosevelt refused to debate Wendell Wilkie in 1940, LBJ refused to debate Barry Goldwater in 1964 and, four years later, Richard Nixon (perhaps recalling his experience in 1960) declined to debate Hubert Humphrey. Indeed, you can argue that the modern American practice of Presidential debates might not exist at all but for the weakness of the position in which Gerald Ford found himself in 1976.

As matters stand, I suspect there will be some reluctance to repeat 2010’s experiment with televised debates between the three principle party leaders. David Cameron will not be inclined to grant Ed Miliband an opportunity to appear Prime Ministerial (whatever that means) though, notionally, a series of debates would, assuming the Lib Dem leader is included, give the government 66% of the airtime to defend its record.