15/07/2016 07:46 BST | Updated 16/07/2017 06:12 BST

Can Theresa May Beat the Replacement Prime Minister Odds?

As the new PM settles in at No.10 there's much speculation about what the future holds for Theresa May. She's made a human shield out of Boris, Davis and Fox in case the Brexit plans end in disaster, but if the past performance of replacement PMs is anything to go by, it still doesn't look promising. In fact, she bears a resemblance to both John Major and Gordon Brown on that front. Especially Brown. Ouch.


Of the 13 PMs since 1950, seven of them resigned in office. That means we've had 6 replacement PMs before May (who is the 7th). There's a striking difference in terms of electability between PMs who make it into office via the traditional route and those who inherit the job. Elected-into-office PMs account for winning 15 of the 18 general elections since 1950. Replacement PMs can only claim 3.

If you dig a little deeper into the numbers, those figures for replacement PMs get worse. Of the last 18 election victories, 12 were won by just 4 candidates (Wilson, Thatcher, Blair and Cameron). How can the remainder of 6 election wins account for 9 prime ministers? That's because 3 former Prime Ministers inherited the job and went on to lose at the polls. That's an electoral failure rate for replacement PMs of a whopping 50%.

Even worse, in some respects, is that of 3 replacement PMs that managed to win an election, 2 of them resigned in office (Eden and Macmillan) during their election winning term. Add them to the electoral failures and that tallies at 4 out of 6 replacement PMs whose careers ended in some sort of political disaster, and 1 (Macmillan) with poor health. Only John Major left the office after winning an election, going full term and losing the next one.

That puts the odds of May winning the next election at evens, and puts a second full term in office at about 5-1 against. Not exactly looking good, is it?

Replacement PMs also claim the 2 shortest stints in office since the war (Alec Douglas-Home and Anthony Eden). Coincidentally Douglas-Home got the top job after beating the most popular contender Rab Butler in 1963. He made Butler Foreign Secretary, a bit like May and Boris, that. Spooky.

Foreign affairs problems are the most common cause of PM resignations (Eden, Thatcher, Blair, Cameron). Economic problems finished Wilson. Churchill and Macmillan had health problems. So roughly 70% of resigning PMs left over foreign policy and the economy. Brexit is nothing but foreign policy and the economy. That doesn't bode well for May.

So what about a replacement PM's effect on their party's fortunes? Again, it's not good news. By far the two longest periods of opposition for both Labour and the Conservatives were preceded by a replacement PM (17 years for Lab after Callaghan, 13 for Cons after Major). Major was an election winner at least, but struggled with a small majority, as May will struggle to beat Labour and the SNP as Brexit legislation passes through the Commons.

As replacement PMs go, perhaps Gordon Brown's circumstances are the closest match to May's. Like Brown, she's succeeding a younger, PR savvy leader who re-invented the party's image as a more youthful political force, and steered them towards the centre ground after over a decade in opposition. She also compares to Cameron much like Brown compared to Blair in terms of her public perception. She, like Brown, isn't one for schmoozing and lacks the easy smiles and slick press conference charisma of her predecessor.

Replacement PMs usually suffer from negative media comparisons with their predecessor because they lack the same election-winning credibility. They were never leader of the opposition, won a TV debate or got the biggest conference applause. Their personal appearance is also relentlessly exploited by the tabloids after a more photogenic predecessor, too. Just consider Brown's wonky eye, slack jaw and fake smile and note the similarities to the photography of May's awkward posture and sour expressions. And a woman is much worse off than a man on that score... Brown's shoes and fertility were never scrutinised by the media, were they?

At least Brown countered his poor media image by citing his role in winning Labour's last 3 majorities. May can't. She helped Cameron limp home with a coalition in 2010, and only a small majority in 2015. On the strength of those numbers alone, Theresa May starts her premiership with less parliamentary clout and public support than Brown had, and even amongst her own MPs, she's worse off than Brown. May had to wait for Osborne and Boris to bow out before she became the top leadership contender whereas Brown was always the most obvious successor to Blair.

So what is May's prognosis? If Brexit goes badly, will May follow suit with Eden and Macmillan and resign? Will someone mount a leadership challenge in 2018/19 claiming she's unelectable? Both look possible. If Brexit goes well, she might see out Cameron's full term, face the polls and win. The odds marginally favour the first two if you want to bet a fiver on it, the last one is at best a coin toss, but a second win after that? Don't bet on it.