New party leaders normally enjoy a honeymoon in the polls. It’s noticeable for leaders taking over in opposition, on the relatively rare occassion that the party leadership changes hands in government the honeymoon is often remarkable. In the last fifty years there have been three previous occasions when the premiership changed hands between-elections:

Wilson-Callaghan, 1976. When Harold Wilson announced his resignation in the middle of March the polls were showing a Conservative lead of between two and five points. The polls immediately following Wilson’s resignation and during Callaghan’s first month in office showed Labour leads of between one and seven points, before returning to a steady Tory lead in May.

When Harold Wilson announced his resignation in the middle of March the polls were showing a Conservative lead of between two and five points. The polls immediately following Wilson’s resignation and during Callaghan’s first month in office showed Labour leads of between one and seven points, before returning to a steady Tory lead in May. Thatcher-Major, 1990. Margaret Thatcher was famously removed by the Tory party in November 1990. In the month before the leadership election Labour had an average poll lead of thirteen points. In the month immediately following her resignation and replacement by John Major the Conservatives had an average lead of five points, peaking at 11 points. Over the next few months the polls settled down to an average Tory lead of four points or so.

Margaret Thatcher was famously removed by the Tory party in November 1990. In the month before the leadership election Labour had an average poll lead of thirteen points. In the month immediately following her resignation and replacement by John Major the Conservatives had an average lead of five points, peaking at 11 points. Over the next few months the polls settled down to an average Tory lead of four points or so. Blair-Brown, 2007. The Blair-Brown handover was a more drawn out affair: Blair announced his resignation at the start of May 2007, when the Conservatives had a poll lead of around six points, and actually handed over to Gordon Brown at the end of June. Through July and August Brown enjoyed an average Labour lead of around five points, peaking in double-digit leads during the Labour conference at the end of September… and their rapid collapse afterwards. The Conservatives were ahead again by October, and remained so for the rest of the Parliament.

Every mid-term change of Prime Minister has been accompanied by a significant boost in polling figures – in the three historical cases, they’ve gone from trailing the opposition to a clear polling lead. The boosts have tended to be comparatively short though – Callaghan and Major only enjoyed a month or so before settling down into a new equilibrium, Brown enjoyed a honeymoon that lasted several months, but that was probably because he was seem to have responded well to the Glasgow Airport attack and Summer floods. There’s no clear pattern as to where the polls settle after the honeymoon: I suppose it depends very much on the leader. Once the honeymoons had passed the change in leader didn’t make that much difference in 1976 and 2007 (in both cases Labour’s position absolutely tanked a few months down the line… but for different reasons), in 1990 though there was a long lasting improvement in Tory support.

So to the current polling position. Today’s ICM poll has topline figures of CON 43%(+4), LAB 27%(-2), LDEM 8%(-1), UKIP 13(-1) (tabs are here). It follows on from an ICM poll last week showing the Conservatives ten points ahead, a YouGov poll giving the Conservtives an eleven point lead and an Opinium poll giving them a more modest six point lead. All four polls had Labour around or just below 30% and the Conservatives nearer 40%, UKIP down a little from the levels of support they’d been showing before the referendum.

Viewed together it certainly looks like the sort of boost a new Prime Minister normally receives, which is a good reason not to read too much into it. New Prime Ministers receive good poll ratings because they haven’t had to annoy too many people yet – the public can project their hopes onto them and convince themselves they really will be different, really will deliver this, that or the other. Before long, however, the shine will come off and they’ll have to start making compromises and disappointing people. This is one good reason for Theresa May not to plan for an early election (and the mistake Gordon Brown made in not shutting down such considerations) – the current polls look wonderful for her, but on past timescales they won’t necessarily be so rosy in a couple of months time. It’s also a crumb of comfort for Labour… though quite a small crumb.

UPDATE: YouGov have fresh voting intention figures that also show a strong lead for the Conservatives, albeit, not quite as big as ICM’s. Their topline figures are CON 40%, LAB 28%, LDEM 8%, UKIP 13%, GRN 4%. Tabs are here