However, there is one man aiming to stand in Cameron's way. In the yellow-and-black corner there stands a political heavyweight of huge influence, one of the archetypical 'big beasts', and an electoral fixture of 25 years' experience: Alan 'Howling Laud' Hope, the leader of the Monster Raving Loony Party.
He's in bullish mood, Hope, when I call him, telling me that the Tories are playing into his hands: Cameron's own slogan, after all, is 'Vote for Hope'. It's almost like he wants to lose his seat.
Howling Laud Hope was one of the founder members of the Official Monster Raving Loony Party, an old friend of its original leader Screaming Lord Such, and a fellow former rock musician. Formerly the party's chairman, he assumed the leadership following the death of Such in 1999, being elected jointly alongside his cat, Cat Mandu, after a hotly contested race. Mandu was killed in a road accident in 2002, and since then Hope has been the OMRLP's sole leader.
Now, he's running against Cameron in Witney, aiming to achieve the hitherto unachieved: retaining his deposit. This has never happened in the party's history; the closest anyone has ever come was Lord Such's 1,114 votes in a by-election in Rotherham in 1994. Hope believes he has a chance - he's gunning for the protest vote, and he thinks this is the climate in which he can win it. But that could present a problem in itself: "We've always said that if any member of the party does manage to retain their deposit, we'll have to throw them out."
Hope has had the rare distincition among Loony Party members of actually entering elected office. He was elected to Ashburton Town Council in 1987, as a member of the Monster Raving Loonies, rising to become mayor in 1998 - 'the silly burghers actually voted me in,' he says. This fact is astonishing when you think about it.
The party is running on an 'anti-government' ticket this year, he says, and they're being ambitious with it.
"If one of us can maybe get three, four or even five thousand votes somewhere and retain our deposit, wouldn't that make the other parties sit up and wonder if they weren't doing something wrong?" he asks.
"Voting for us is not a wasted vote; the only wasted vote is one that doesn't get used. The majority of people in this country don't bother to vote, and if all the people who don't vote voted for us, we'd be in Government."
His party's key manifesto pledges this time around demonstrate an imaginative line in out-of-the-box thinking. Demonstrating a keen ear for issues in the economy, social justice and the environment, they're campaigning, for instance, for the introduction of a 99p coin to reduce wastage.
Then there's the idea that all new-builds will be fitted with air-con on their outside as a way of thwarting global warming. Controversially, they're also planning to ban terrorists from having beards.
Tellingly, some of their previous campaigns' election pledges have made it into the statute books. Most notably, shifting the voting age to 18 and all-day pub opening. In 2005, they tried to scrap MPs' expense accounts, wanting to redistribute it to the poor, 'so they could waste it instead'.
For this year only, the party has been renamed the Monster Raving William Hill Party. The betting company has chosen to sponsor the Loonies this year. Is this a cheapening of the political process?
"Cheapening? Cheapening?" he expostulates. After what all those MPs have been getting up to?"
Hope is also 'very upset' that he hasn't been invited to take part in any of the forthcoming leaders' debates on television. He's not the only one: he tells me of a Facebook group with more than 2,000 members who think the same. Sadly, it seems he's destined to stand forever outside the establishment, as one of the UK's true political mavericks.