We live in a presidential political culture. The next general election will be billed as a battle between David Cameron and Ed Miliband, the only two candidates with a chance of being prime minister. Few others will get much of a look-in. As they prepare for the presidential battle ahead, both turn to the US for inspiration. Miliband hires David Axelrod, one of President Barack Obama’s strategic superstars. Cameron has acquired the services of Jim Messina, Obama’s 2012 campaign manager. Allies of a victorious president can make big money advising other potential presidential figures.

There is, though, a twist. Britain does not elect presidents. Parties are fragile beasts, but Britain is still a party-based system. Most days of the week I read commentators wondering why Labour leads in the polls when Miliband’s personal ratings are so low. Some answer by pointing to the 1979 election, when Margaret Thatcher’s ratings were well below those of her main opponent, Jim Callaghan. She still won. And 1979 is not the only example. Contrary to mythology, in British general elections, leaders are never pivotal in determining the outcome. The context in which they lead is much more decisive, a background over which leaders have only limited power to shape.

Let us take a brief tour of recent elections to prove my point. Labour’s defeats in the 1983 and 1987 elections, even the scale of the slaughter, had little to do with Michael Foot, Neil Kinnock or the victorious Thatcher. The left of centre was split in two, a formal schism that made it impossible for either Labour or the Social Democratic Party (SDP) to win. Indeed I recall reading as a student a prophetic letter in the Guardian in 1981: “Shirley Williams has left the Labour party to join the SDP. Margaret Thatcher will rule for another 10 years.” Thatcher’s genius was not winning elections, but in recognising she had rare political space to act radically. If Labour had a popular titan fighting the 1983 and 1987 elections it would still have lost. Labour was impossibly split over all the big issues from that era.

This happens to parties sometimes and, as a result of the divisions, they become impossible to lead. Parties that are impossible to lead are unelectable. The Conservatives were unleadable in the 1990s. Before Tony Blair became Labour’s leader, the Conservative government was falling apart over Europe. Blair’s predecessor, Smith, would have won easily in 1997 partly because the Conservatives could not win. Some of their MPs looked forward to defeat, a reliable sign that something is not right with a party.

Oddly, I sense that almost two decades later, a few Conservative MPs do not want Cameron to win the next election, or at least they do not ache for him to do so. The persistent unruliness in the Conservative party, though less marked than in the late 1990s, will be an important factor at the next election. There is nothing Cameron can do about it. His party happens to be quite unruly. The phase will pass but not for some time yet.

Returning to our brief tour, the Tories’ slaughter in 2001 had little to do with its leader, William Hague. The moment Hague ceased to be his party’s leader he became popular. On one BBC phone-in, callers pleaded with the former leader to become his party’s next leader, a contortion that Hague noted with self-deprecating wit. No one noticed his wit when he was leader. The political context destroyed him and rendered him weird. Once he had escaped the context he became authoritative.

The following election in 2005 took place after Iraq. Blair was Labour’s leader but was no longer regarded as a winner. Instead his more popular chancellor, Gordon Brown, was summoned from moody exile in Scotland to front the campaign. The two of them were filmed having ice-creams together, by then an unlikely double act pretending to be having fun. But it was the double act that mattered in influencing the outcome of the election, not the leader.

Arguably the one exception to my rule is the 1992 election, which John Major won as a new leader against Kinnock, who had led in opposition for nine years too long to be electable. But even this example is not clear-cut. The only other Labour leader would have been John Smith, the architect of the alternative budget unleashed at the start of the election and a gift for the Conservatives. Major was a comically poor campaigner, looking silly on his soapbox. He was not the decisive factor in 1992. Smith would not have been if he had replaced Kinnock.

The current context is unusually mixed, which is why the next election will be close. Miliband is a relatively lucky leader. When he won the contest some argued he would be “Labour’s Hague”. There was never a chance of this. Miliband became leader in a hung parliament in the midst of economic fragility, with the Liberal Democrats losing support to Labour the moment they joined the coalition. As a big bonus for him, Cameron faces a tough context, Ukip breathing down his neck on the right and the Lib Dems showing some signs of remaining robust in the south of England as demonstrated by their victory in the Eastleigh by-election. Cameron is an unlucky leader.

The potent counter for him comes in the form of the recent past, the most emotive terrain in politics. Polls suggest Labour is blamed and not forgiven for the apocalyptic crash of 2008. It was easy for Blair/Brown to partially disown their party’s governing past. They created a chronological divide between old and new from a safe distance. By 1997 Labour had not been in power for almost 20 years. The economic crash is a recent event. It would still be a recent event if Labour had another leader.

No doubt Labour has hired Axelrod partly in the hope he can improve Miliband’s ratings. Labour’s election chief, Douglas Alexander, has been known to reflect that the campaign is bound to focus on its leader and on virtually no one else in his party’s ranks.

I predict Axelrod will not turn Miliband into Obama, and Cameron’s personal ratings will remain quite high. But I also predict the outcome of the election will be determined by other factors.

— Guardian News and Media Ltd

Steve Richards is a political columnist and broadcaster. His book on New Labour, Whatever It Takes, was turned into a Radio 4 series. Steve Richards will present Rock’n’Roll Politics at Kings Place, central London, on April 28.