Britain's Prime Minister David Cameron leaves 10 Downing Street to attend Prime Minister's Question Time in Parliament, in London March 25, 2015. Image Credit: REUTERS

One way to tell that something has taken Westminster by surprise is when everyone claims to have known it all along. British Prime Minister David Cameron was never going to serve three terms. He is lucky to have made it through one and voters have not yet approved his application for another.

On current polling, the Tories’ best hope in the election is to be the largest party in a hung parliament. Cameron would then have to persuade other parties to support his legislative programme while keeping a lid on roiling backbench fury at his failure to have won a majority. Again.

If he survives all that, the hobbled prime minister would then have to renegotiate Britain’s membership of the European Union and put it to a referendum no later than autumn 2017. That process would evacuate any residue of tolerance that Tory Eurosceptics might have had for Cameron. Support for the “in” campaign would be his valediction.

So Tory MPs long ago pencilled in 2018 as the latest likely date for a leadership contest. That is two years earlier than the election in which Cameron declared on Monday he would not be running. That evening, Michael Gove, spraying cool nonchalance on the rising flames of media excitement, said it had been “a statement of the bleeding obvious”. Which it had, up to a point.

It was obvious to the kind of person who runs war games of party leadership scenarios the way football fans study fixture lists to predict their team’s progress. That is not most people.

So, paradoxically, the prime minister made big news by saying something that was old news to the people who decide what is news. To make the non-news even newsier, Cameron went so far as to name contenders in the succession race — Theresa May, George Osborne, Boris Johnson — as if no one had noticed them limbering up next to the running track.

So what has changed? Sometimes we only see the gap between what is presumed and what is confirmed once it has closed. Politicians want to keep their options open, while their enemies and events conspire to shut their options down. A lot of politics is defined by the tension between those forces. (Consider, for example, Ed Miliband trying to appear as if he is ruling out a deal with Scottish nationalists without slamming shut a door that may one day lead him to Downing Street.)

Although a third Cameron term was not seriously on the cards, ruling it out still looks like a bow to pressure. Why eliminate ambiguity? It has a whiff of capitulation. It could have been unguarded chatter but I doubt it. No prime minister does an interview on the eve of a general election campaign without a script and few politicians (Boris is one) rival Cameron’s thespian polish, making scripted lines sound spontaneous.

The aides who accompany Cameron from one public event to another know verbatim the answers he will give to almost any question. Then there was the cute simile for prime ministerial terms — like shredded wheat, two are satisfying and three are too many. It suggests attention to the nuance of how the message should be delivered. But who was the intended audience?

Perhaps he has made a tactical concession early, offering himself as a glorified caretaker to get the European Union (EU) referendum done.

Partly, Cameron is conducting coded negotiations with his own party. If the prospect of a majority is receding, he needs to avert the regicidal rumblings that could begin within hours of the results being declared. So perhaps he has made a tactical concession early, offering himself as a glorified caretaker leader to get the EU referendum done. It will be a bloody business and potential leadership challengers have an interest in waiting until it is out of the way: Let Cameron martyr himself in Tory Euro-troubles, then take over for post-war reconstruction.

To make a virtue of necessity, Cameron hopes that signalling readiness to stand aside will project healthy detachment from the unseemly scrum of day-to-day politics. No 10 strategists want to position him as a family man who feels duty-bound to stay in office, but just for as long as it takes to complete his self-declared economic rescue mission. After one term it is only half-accomplished. (A veil of economic excuses is drawn over the broken promise that the budget deficit would be fixed by now.) So the message is meant to be that Cameron is the pragmatic choice, somehow less political than the sweaty-palmed fanatics leading other parties.

One virtue of Cameron’s claim not to have any Thatcheresque urge to go on and on is that it is true. Thoughtful observers in the Labour party concede that the Tory leader’s ability to look unruffled by the job, in marked contrast with his predecessor, is an asset. They believe him when he says he would rather quit and get on with his life than cling on at the expense of dignity and sanity.

One unwritten law of Downing Street is that the trait for which prime ministers end up being despised is an inversion of whatever it was that was once the source of their appeal. Margaret Thatcher’s fixity of purpose became monstrous stubbornness. Tony Blair’s easy charm soured to snake oil salesmanship. As chancellor, Gordon Brown was admired for seriousness that turned out to be alienating coldness in a prime minister. For Cameron, it is the easy way he wears power like a bespoke suit. On a good day, that inspires confidence; on a bad day it reeks of entitlement. Depending on the context, he projects moderation, complacency, pragmatism or arrogance.

If ruling out a third term before winning a second has any impact on public opinion it will be to illuminate whichever face of Cameron voters see already. The prime minister’s allies offer it as a mark of his level-headedness: Neither intoxicated by power nor addicted to it; a natural leader. Labour want it to reveal his worst side: Taking voters for granted; presuming the top job is his by right, to own and pass on at will. Those are positive and negative charges of same force.

It may not turn against him before the election, but it will be his eventual undoing. If he survives the election, destructive speculation about when he plans to go will begin immediately. The problem with looking too cavalier about power is that people start to think you do not deserve it.

— Guardian News & Media Ltd