Mr Cameron has chosen a date for his departure: his closest allies in Downing Street have been told that he intends to announce he’s leaving in the spring of 2019. The Tory leadership race would then take place over the summer, with the new leader introducing themself to the country at the party conference that autumn.
Out of post-war Prime Ministers, Cameron has already served longer than Winston Churchill (considering solely his post-war premiership), Anthony Eden, Alec Douglas-Home, Ted Heath, Jim Callaghan and Gordon Brown. He overtakes:
- Clement Attlee on 11 August 2016
- John Major on 14 October 2016
- Harold Macmillan on 16 February 2017
- Harold Wilson on 14 February 2018
- Tony Blair on 6 July 2020
- Margaret Thatcher on 6 December 2021
A Conservative leadership race over the summer of 2019, with the new leader making his or her first appearance at the October conference, sounds intriguing. But there are a couple of problems with timing.
A modern-style leadership race takes about 2 months, so this is time taken out while a party should be preparing for the next election - due on Thursday, 7 May 2020. If we look at how far in to a Parliament a Prime Minister has resigned (for whatever reason) we have:
|General election||Change of leader||Outgoing leader||Incoming leader||Time from election|
|October 1951||April 1955||Churchill||Eden||3y 5m|
|May 1955||January 1957||Eden||Macmillan||1y 7m|
|October 1959||October 1963||Macmillan||Douglas-Hone||4y 0m|
|February 1974||April 1976||Wilson||Callaghan||2y 1m|
|June 1987||November 1990||Thatcher||Major||3y 5m|
|May 2005||June 2007||Blair||Brown||2y 2m|
The only example of a change of Prime Minister in the fifth year of a Parliament didn't work out well, but the two fourth-year changes did lead to the party winning the following general election. Interestingly, these were around the same point of a Parliament, and - if the change were at a similar point - then a new leader would present himself or herself at the 2018 conference. At this point, Cameron would have become the third longest-serving post-war Prime Minister.
It is possible that the Conservatives will enter Opposition after the next election, and - if Labour wins decisively - the removal vans could be at 10 Downing Street by lunchtime on Friday, 8 May. Now consider the scenario of a new leader being unveiled and taking office at the 2019 Conference, which we can reasonably assume will be in October. If the new leader takes office on or after 11 October 2019, then he or she runs a real risk of having a shorter premiership than Bonar Law's. So, I think we can rule out a leadership change that late in 2019 - and remember this would involve the starting gun being fired in July or August.
If the 2014 pattern is followed, then the European elections will be on Thursday, 23 May 2019. The 2014 election saw the Conservatives come third, on 23.93% of the vote - their worst result ever in a national election. Unless the Conservatives are very unlucky, then there will be a dead cat bounce, and Cameron can say that he increased the party vote. With general elections now being on a 5-year cycle, the European elections are the last major test of party support.
Cameron could announce his resignation following the European elections, leaving on an electoral upswing, and a new Prime Minister being chosen in August, ready to face the House of Commons when the summer recess is over.
Alongside the European elections, there would also be the local elections, and - due to these being on a 4-year cycle - those elected alongside the May 2015 general election will face re-election.
The European and local elections will be the major elections of 2019, and it would not do for the Conservatives to be in the middle of a leadership contest (although in 1994, Labour - by tragedy, not by choice - had to fight the local and European elections while its leadership contest was happening). Again, if we assume that a contest, from start to finish, is 2 months, then this would mean Cameron announcing in March (around the Budget?) at the latest that he would be going and setting the contest in process.
In 1955, Eden decided to cut-and-run, with Parliament dissolved exactly a month after he took office. Major decided to take the opposite approach, and nearly finished the complete term that Thatcher had led the Conservatives to. An incoming Prime Minister wanting the same (or larger) gap between taking office and fighting his or her first election as Prime Minister - with enough time to establish a distinct style - would need to take office by 27 December 2018.
Looking at the dates, I think that Cameron will either step down in 2018 or be leading the Conservatives into the 2020 election.