Is Nick Clegg the British Barack Obama? Photomontage: Steve Caplin

For Barack Obama, the crucial moment came one cold night in January 2008, when the one-term senator's unexpectedly decisive triumph in the Iowa caucuses set him on the path to an epoch-making victory. For Nick Clegg, it happened last week, when he stepped back from his debate podium to address a retired toxicologist from Cheshire.

Obama promised to transcend America's troubled racial past and the culture wars of the 1960s. Clegg promises to make the drivers of night buses let you get off between stops, and to refund VAT to mountain rescue services. (Oh, and cut taxes on low earners, break up the banks, and scrap the Trident replacement.) From Yeovil to Cornwall, from northern Bristol to certain areas of Surrey, there is a frisson, a whisper of possibility: Yes, we can. Well, maybe. And probably not, actually, because of the first-past-the-post voting system. And yet you can feel it in the air: the fierce urgency of Nick; the audacity of Clegg.

It was always inevitable that Obama would cast a long shadow over this election, inspiring activists across the spectrum to exploit internet campaigning, small-scale fundraising, and the intoxicating promise of unity and change. But it was the perpetually tieless David Cameron, we had assumed, who would seek most directly, if also most cringe-inducingly, to appropriate the president's mantle. We were wrong.

Consider the Obama-Clegg parallels. Obama's sensibility developed during a childhood dominated by the absence of his father and his struggles to fit into communities in Hawaii and Indonesia; Clegg's outlook was forged in the crucible of his hardscrabble origins in Chalfont St Giles, Buckinghamshire, his education at Westminster School in London, and his degree in archaeology and anthropology at Robinson College, Cambridge. Obama had "Yes, we can". Clegg has "I agree with Nick". Obama, as a youth, flirted with hard drugs. Clegg set fire to a cactus.

These parallels aren't perfect, of course. They may even strike some readers as absurd. But what Clegg's rightwing and leftwing critics miss, as do predictably sarcastic journalists, is that this is precisely the point. To say that Nick Clegg is the British Barack Obama is not to suggest that he is an exact duplicate of the original, American Obama, transplanted to our shores. He's a British version. The US likes its heroes to be inspiring underdogs who battle vast forces to realise their dreams. We like ours to be not-particularly-inspiring underdogs who never do quite realise their dreams – think Eddie "The Eagle" Edwards, or Mallory on Everest, or the Beagle 2 Mars probe. Thanks to various unfortunate psephological realities, Nick Clegg almost certainly won't realise his dreams either.

Just like Obama, Clegg even has his own squadron of loopy conspiracy theorists, intent on inadvertently bolstering his support by wheeling out implausible claims about his origins. In America, the "birthers" say that Obama is Kenyan-born, and/or a Muslim, and/or that his birth certificate was faked; in Britain this weekend, the Mail on Sunday published a surreally xenophobic sneer at "the United Nations of Nick Clegg", implying that his Spanish wife, Dutch mother and half-Russian father meant that he failed to meet some obscure and rather distasteful blood-based definition of Britishness. In an echo of the non-existent Michelle Obama "whitey" tape, we can presumably soon expect a report on Clegg's plans to ban Christmas, or to force Britain's motorists to marry gays.

Impressionists and caricaturists, meanwhile, complain that they can't properly satirise Clegg, because he has few distinguishing features. But that, again, is the point: Clegg has a transparent quality, a nondescriptness, that allows each of us to project on to him our deepest aspirations. These last few days of Cleggmania have seen him compared also to Winston Churchill, the epitome of British stubbornness – one poll suggested that Clegg was the most popular party leader since Churchill – and to Che Guevara, the epitome of stylish beret-wearing.

But these are inevitably imperfect efforts to capture in visual form the unique charisma, the indefinable Clegginess of Clegg. Ultimately, that can't be done. His qualities are too hard to pin down: Nick Clegg looks kind of normal, he wears normal-looking clothes, he has some good ideas, along with a few that are a bit rubbish; he might do OK, but if we're honest, probably not brilliantly, and he has provoked a low-key outburst of restrained hysteria. He is a British version of Barack Obama, but perhaps this is just another way of saying that he is the new Tim Henman.