As TV debate postmortems continue into the weekend, we would do well to step back and ask ourselves a simple question — one that’s far more fundamental than who won and who lost on Thursday night. Do party leaders really matter when it comes to people deciding which way to vote?

The answer, at least according to decades of research by political scientists, can be summed up as follows. Leaders probably do matter. But they matter more to some voters than to others, they matter more in some countries than in others — and we are still arguing about precisely how much they matter.

Some people, it seems, are more easily swayed by leaders than others. If you are not particularly into politics, if you don’t identify very strongly with any of the parties, and if you watch a lot of television, then there’s more chance that your vote will be influenced by the men and women at the top. Given that all this is true of a large, maybe even an increasing, number of UK voters, then, clearly, leader effects in this general election cannot be easily dismissed.

On the other hand, those effects are mitigated by context. Leaders seem to matter a little less in parliamentary than in presidential systems, in media environments where the tone is set by public rather than purely commercial broadcasters, and in political cultures that can be characterised as consensual rather than majoritarian.

Even after five years of coalition government, one would be hard-pressed to classify the UK along with Europe’s Nordic or Germanic polities, where compromise is prized above winner-takes-all. But given the UK is a parliamentary democracy where television’s treatment of politics continues to assume it should educate as well as entertain, then even those leaders with a realistic chance of running the country are unlikely to have as much influence on voters as their US counterparts.

Just as importantly, as Ohio State University’s Anthony Mughan stresses in a recent academic article, voters do not (because realistically they cannot) completely separate leaders from their parties. Nor, for that matter, can they possibly judge one leader without at least implicitly comparing them to their opponents.

As a result, the chances of a voter deciding to change their vote simply because they are impressed by one party’s leader are slimmer than is often assumed. For that to happen, said leader, especially if their party is not highly regarded and especially if their opponents are not utterly hopeless, has to be very impressive indeed — which is why the Conservatives may end up disappointed if they attempt to frame this election as all about a choice, not just between competence and chaos, but between David “when it comes to who’s prime minister, the personal is national” Cameron and Ed “just not up to it” Miliband.

Neither during the first week of the campaign proper, nor in either of the televised showdowns, has Mr Cameron stood so head-and-shoulders above everyone else that thousands, let alone millions, of voters who might otherwise have steered clear will be flocking to his party.

Indeed, detailed polling suggests that it is Mr Miliband who has done himself and his party a few favours, managing to significantly erode (although not to completely override) widespread doubts about his strength, his decisiveness, and whether he would be up to the job of prime minister.

Moreover, he seems to have managed this at the same time as strengthening his claim — an important one for challengers, research suggests — that he is more “in touch” with the electorate than the incumbent.

Tory strategists will hope that this is a one-off boost rather than the beginning of a trend. They will also hope that Nicola Sturgeon’s impressive turn on Thursday night doesn’t blunt their bid to persuade the English electorate that the SNP should have no part to play in governing at Westminster as well as Holyrood. If they are wrong, then they could be in serious trouble.

[Originally published at http://www.ft.com/cms/s/0/a3e07878-d9f7-11e4-9b1c-00144feab7de.html]