David Cameron’s term limit is admission of weakness and a tactic to maximise the Tory vote

The message is now clearer and louder: Vote Dave, Get Boris

David Cameron is interviewed by the BBC's James Landale (BBC)

What did David Cameron mean by ruling out a third term as Prime Minister? Above, with James Landale of the BBC in the Camerons’ Cotswold kitchen. (And is that a red chopping board with “Calm Down Dear” on it?)

My guess is that, having already said (to Matthew d’Ancona) that he didn’t fancy being Prime Minister for more than two terms, Cameron thought that he would gain two things by being definite:

(a) Modesty. People don’t like the idea of a leader going on and on. They agree with the Shredded Wheat analogy: two parliamentary terms is about right; three is too much.

(b) Boris. It draws attention to other strong Conservatives, particularly the Mayor of London, who is the only politician in the country with a net positive rating. Vote Dave, Get Boris is not a bad line. Just as Vote Blair, Get Brown worked for Labour in 2005.

The alternative is to say that you are putting yourself forward for a full term, you take nothing for granted and if you win the election you’ll worry about the future then. That leads to “on and on” speculation on top of speculation about who would be the next Tory leader, of which there would be plenty regardless.

So I suspect Cameron’s line is quite deliberate – not that I think that Landale was put up to it, but I think the Prime Minister intended to rule out a third term at some point early in the election campaign.

It is, however, a product of weakness and a recognition that he needs to try everything to increase his vote, just as Blair’s decision was in 2004. It worked for Blair – many people have forgotten that brief period when Brown was more popular than him – but of course it caused no end of trouble as soon as the election was out of the way.

I guess that Cameron has made a similar calculation. Throw everything at the election and worry about the consequences later. But there is one post-election problem with which this helps. If he holds on as Prime Minister, his next priority will be the referendum on Britain’s membership of the European Union. It makes sense to take his own future out of the referendum campaign. It has long been speculated that his plan would be to win the referendum to stay in (a cosmetically reformed) EU and then to stand down. Now he has confirmed it.

The rumble of the approaching storm that is Boris Johnson, about to make landfall at Uxbridge, has just got louder.