You don’t have to be mad to be PM — but it helps!

DAVID Cameron confirms he won’t seek a third term as Prime Minister. ‘ He will be the first Prime Minister not to go mad in Downing Street since Jim Callaghan,’ one of his ‘closest allies’ advises the Sunday Times.

A large claim to make. No wonder the ally prefers to remain anonymous.

So Cameron’s Tory predecessors Margaret Thatcher and John Major are barking, along with Labour’s Tony Blair and Gordon Brown?

Cameron presents himself as a down-to-earth type who has a job to do and who’ll have no difficulty moving on when it’s finished. But don’t all premiers see themselves in this way?

Thatcher’s three election victories made her think herself special, that her reign must go ‘ on and on’, but she wasn’t mad.

Ambitious Tories seeking cheaply the power she worked hard to acquire say this to diminish her achievements and make themselves seem superior.

She altered our political landscape, changing Labour as well as the Tories. So it was natural for her to worry that her successors would revert to their wet old ways if she quit prematurely. It turned out she was right about that.

Major’s paranoia about being surrounded by enemies — the Eurosceptic Tory MP ‘bastards’ pressuring him over the EU — helped unravel his premiership and did make him seem a bit unhinged towards the end.

But his anger was rational, not mad. He was the victim of plotters. (Canoodling with Edwina Currie seems mad, but only in the sense that it was out- of- character in so discreet and controlled a man.)

Blair was ‘mad’ in the same way as Thatcher — ie, messianic, believing after his electoral victories that he was special. But his courtship of Right-wing U.S. president George W. Bush and his ‘mad’ agreement to join the U.S.’s invasion of Iraq raised his international profile and is the source of his family’s great wealth today.

Brown’s long belief that he was destined to lead Labour, and open craving for the job, was unbalanced but not mad. His feverish scheming to get the top job turned him from plotter to plotting victim, as Blairite knives came out against him.

Will history be kinder to his memory? The Nobel Prize-winning American economist and commentator Paul Krugman said Gordon ‘saved the world’ by acting decisively after the 2008 crash.

So is Cameron the sanest PM since 1976-1979 Labour premier James Callaghan? On the credit side, he doesn’t have Thatcher’s goggle-eyed idealogical certainty. Nor does he exhibit the bateyness over party plotters that damaged John Major. True, his enthusiasm for driving Libya’s despot Muammar Gaddafi from power recalled Blair and Saddam Hussein. However, there have been no reports of him descending into mobile phone-throwing No 10 tantrums al la Gordon Brown.

WE WON’T really know what Dave was like as PM until he’s out of No 10 and no longer in a position to help the careers of those who’ve observed his day-to-day behaviour. But surely enough is known now to form the foundation of future ‘Dave was batty’ stories. His early PR wheezes to demonstrate concern for the planet and the less fortunate — a windmill on the roof of his London house, photoops hugging huskies and ‘hoodies’ — certainly had a touch of the absurd.

His apparent need to be surrounded by fellow Old Etonians — ‘Lord Snooty and his chums’ transferred from cartoon to No 10 — is eccentric, to put it mildly.

Drawn to exotic/edgy characters like Camila Batmanghelidjh, of Kids Company, and, despite warnings, to raffish, former News Of The World editor Andy Coulson, there’s a flaky side to Cameron at odds with his down-to-earth pretensions.

I’m teasing, of course. But ‘the first prime minister not to go mad since Jim Callaghan’ is quite a boast — and there’s still plenty of time until 2020, his depature date.

Surely the truth is all prime ministers seem mad when they exhibit perfectly normal human traits while imprisoned in the straitjacket of power.

Publicly they must pretend to be above the needs, appetites and pretensions of ordinary mortals lest we lose faith in their ability to govern us.

They don’t have to be mad — but it helps.