What do Winston Churchill, Margaret Thatcher, and Nelson Mandela all have in common? According to a poll by BritainThinks, they are the individuals who best embody the most important qualities of leadership.

It’s not a photo finish. Churchill is in a league of his own, head and shoulders above the rest. That’s why we created the Churchill Index to see how other leaders – past and present – measure up, particularly on the top three attributes: great communication, decisiveness and integrity.

It seems they don’t make them like they used to. With Churchill’s total scores on the top three attributes rebased as 100, David Cameron makes it only halfway up the scale at 44.94 – behind Barack Obama and Angela Merkel, Alex Ferguson and Alan Sugar – but ahead of Tony Blair, Nicola Sturgeon and Nigel Farage (and well ahead of Tory leadership contenders Theresa May, Boris Johnson, and George Osborne). Jeremy Corbyn languishes in second-last position, scoring 21.35 and able to beat only Russell Brand.

As Cameron marks 10 years as Tory leader, our poll reveals that he is seen as decisive and as having the courage to see his decisions through. His communication skills are admired and his judgment is trusted on crucial policy areas such as the economy, national security and the EU. Of the UK party leaders, Corbyn, almost 100 days into his leadership, is the one most closely associated with having integrity. He is also thought most likely to put the interests of working people first and is ahead (just) on protecting public services. Less positively, however, he is seen to be less able to take the necessary tough decisions and, overall, is seen as a less effective leader than Cameron (and, indeed, Ed Miliband when we conducted this survey in 2012).

BritainThinks convened a focus group of swing voters to help dig a bit deeper into these impressions. Although they told us that Cameron was much more impressive than other contemporary party leaders (“No one apart from him looks, speaks, walks or talks like a leader”), the verdict is that he is “the best of a bad bunch”. He is seen as a skilful operator and a reliable pragmatist, but is also thought to lack empathy or a real understanding of how ordinary people live. Described as cunning, he is felt to lack integrity; when voters were asked which animal best represented his personal qualities, the most common choice was fox.

Corbyn seems more sincere and, for some, more likeable but this is not, in the eyes of these swing voters, enough to make him a leader. One said: “He does talk like a normal person … but he has no gravitas and doesn’t inspire people.” Some worry about his lack of experience and naivety. This manifests itself in policy positions that, at best, they disagree with (not singing the national anthem has stuck as a symbol of his “otherness”) and, at worst, may be dangerous. On the topic of national security, one swing voter wryly observed: “Corbyn would probably have a nice cup of tea with Isis and think he could talk them around. He’s inexperienced and he’s a pacifist. That’s fine until you have to deal with people.”

It is the SNP’s Sturgeon, rather than Corbyn, who is seen to run Cameron most closely. She is admired as strong, principled and able – but (at least for the English swing voters) is also thought to have excessive focus on Scotland, to be “zealous” in fighting for Scottish priorities and, as such, has little to offer them. Farage was seen by most as direct, strong and clear – but also as divisive, with many disagreeing strongly with his views and describing him as “smug” and “sleazy”.

We also explored perceptions of some of the most talked about future leaders of both main parties, but the findings offer little comfort to either. Of the Westminster village’s anointed Labour hopefuls, Tom Watson, Dan Jarvis and Lisa Nandy were unknown to swing voters while even those who have cut through a little – such as Chuka Umunna – have yet to have significant impact. Only David Miliband was both well known and able to create a positive reputation, but voters do not expect him to stand as a future candidate. Hilary Benn was not mentioned, but these groups were before last week’s parliamentary debate on Syrian airstrikes. It remains to be seen if that will be as game changing as many of his colleagues hope. The new Liberal Democrat leader, Tim Farron, barely registered.

The Tory contenders were better known but less popular. There was little warmth towards May, who was seen as “cut-throat” and “annoying”, while Osborne was “sly” and “unpopular” (with none of his colleagues’ belief in his strategic brilliance acknowledged by voters). Johnson scores well on likeability, but, ironically, this author of a book about Churchill’s greatness is too easily dismissed as a joker to come close to matching his idol.

Deborah Mattinson is founding director of BritainThinks