Fascinatingly, the whole thing is being organised by John B Emerson, a prominent Clinton-ite and close friend of Bill. Either this suggests that Hillary's supporters are finally settling their differences with the Obama camp, or that Mr Emerson knows which side his bread is buttered on. But I digress.

The really, really interesting thing about Obama's coming Hollywood fundraiser is what its surprisingly low key nature tells us about the Democrat campaign's attitude towards all those fawning Hollywood superstars who have helped grease its financial wheels.

In recent weeks, Scarlett Johansson has gushed that her "heart belongs to Obama" and expressed "amazement" that he returns her emails. Ben Affleck has declared that "Hollywood loves Obama".  The rap artist Nas has released a song in his honour, while P Diddy, Jessica Biel, Robert De Niro, Dennis Hopper, the Black-Eyed Peas, Chuck Berry, Laurence Fishburne and, well, almost every properly famous face in town has jumped aboard his bandwagon.

Yet look for celebrity endorsements on the Obama website, and you'll find nothing. Not a single word of praise from any common-or-garden film star. And when you consider the strangely low-key way Tuesday's event is being organised, you get the impression that this has been done as part of a deliberate policy.

First, only between 500 and 800 guests will attend, a bizarrely low number for this stage of a campaign (when the candidate is usually able to fill football stadiums). Secondly, Obama will only be hanging around LA for (at most) three hours, and no photo-calls are planned. Thirdly, it looks like he'll be leaving Michelle at home (she's not mentioned on the invite). And fourthly, there's no word on whether TV cameras will be invited to hear him speak.

Contrast that to when Obama visits, say, the Deep South. Then, half the state is invited to the local park or sports-ground to give him the reception of a rock star. The two scenarios are so strikingly different that it suggests America's would-be next President is trying to deliberately underplay his celebrity connections.

There's probably a good reason for this. At the last two elections, Al Gore and John Kerry made great hay out of their film-star links, and a fat lot of good it did their campaigns. In fact, all the polling evidence suggests that being the darling of the so-called Hollywood liberals is these days likely to actually damage a Democratic candidate's performance in crucial swing states.

This sounds counter-intuitive but fame is a more tarnished commodity than it used to be. And get this: according to the LA rumour mill, Obama has actively turned down assistance from members of the local show-business fraternity – George Clooney, who recently offered to host a gala dinner on his behalf, was apparently told "thanks but no thanks" by Obama's campaign manager David Axelrod.

Scarlett Johansson, meanwhile, has been kindly asked not to issue any more gushing praise of hero (at least not in public) and other celebrity fans who have offered to "speak out" in Obama's campaign have instead been quietly asked to make an anonymous financial donation.

In effect, as plans for next week's event indicate, Barack Obama would like to use Hollywood like a piggy-bank. Or, actually, a high-street pawnbroker: somewhere he can quietly pop to when he runs short of cash, but not the sort of place where he wants to spend very much time - and definitely a location to avoid being seen in.

It's a funny world, when famous folk - who have added stardust to the campaigns of potential presidents since the days of JFK - are considered to be an electoral liability. But in this, as in a growing number of its defining features, election 2008 is turning accepted wisdom on its head. And America might just be the better for it.