In response to the latest mild gossip about highly hypothetical leadership challenges to Cameron we've had the usual chorus of responses: "Have the Tories learned nothing?", "Do these Right-wingers not comprehend that Cameron's failing has been not to drag his party enough to the centre, not dragging it too far!" and most commonly of all "How can Conservatives so easily forget that split parties do not win General Elections?"
This last claim is made so ubiquitously and with such confidence that it's easy to forget that it's total nonsense. Did massive mid-term splits in 1980 and 1981 stop the Conservatives winning in 1983? Did the Conservative Party being so split that it deposed a sitting Prime Minister stop the Conservatives winning in 1992? Has there ever been a more split Cabinet than Wilson's in 1974, but did that stop him from winning the October 1974 General Election?
Many of those that first pressed this claim did so to demand loyalty to Major in the mid-1990s, conveniently forgetting that they themselves had been plotters against Thatcher in the late 1980s. People say: "Did the 1995 leadership election help Conservative fortunes in 1997?" But what they forget is that the rebellion failed and so policy didn't change. The 1997 defeat was multi-dimensional and Conservative rebellions probably played only a minor role, but insofar as they did make a difference the difference they made was to secure Major's position and an essentially unchanged failing political strategy.
Some readers will say: "Ah, but opinion polls reveal that voters dislike split parties!" That's doubtless true, but what they like even less is clearly bad policies. Voters surely dislike splits primarily because when a party is split voters will be unclear what is stands for and what policies it might enact. A party united behind bad policies presents voters with no such ambiguity, and so voters can decide, with clarity and confidence, that they don't like it and are going to support someone else.
Mid-term splits in parties are a key part of debate in a Parliamentary democracy. We don't determine policy by opinion poll, and we don't elect Prime Ministers for a term. MPs are elected for four or five years and in that time it is their job to determine (or technically to advise the Queen as to) who will be Prime Minister and what policies will be brought in. The modern notion that a General Election manifesto should contain a list of policy promises which it is the elected government's task to enact is a perversion of Parliamentary democracy. A party is fundamentally a collection of MPs within Parliament, and those MPs must in the last analysis determine who leads them. Mr Cameron will be standing in only one constituency at the next General Election, answerable to only one constituency's-worth of voters.
None of this implies that Cameron will be or should be deposed. But it's just not true that mid-term splits lose General Elections. It's bad policies and poor political strategies that do that.