John McCain’s campaign has asked a Hollywood agent to sprinkle some glitter over his anointment as the Republican nominee - while Barack Obama frets about celebrities stampeding towards the Democratic convention in Denver next week.

Even Arnold Schwarzenegger, California’s Republican governor and former action movie star, has stalled on accepting a prime time speaking slot at McCain’s convention in St Paul next month. He may even skip the event all together because of his state’s budget crisis.

Jeffrey Barry of the William Morris agency is reported to have been engaged to make the Republican convention in Minnesota shine a little brighter. So far the headline act at the event’s “kick off” party is expected to be the ageing Beach Boys band. Mr Barry is said to have signed up “Redneck Woman” singer Gretchen Wilson for an event on September 2.

But the Republicans are heavily reliant on Country & Western talent with other names scheduled to appear including John Rich, Cowboy Troy, LeAann Rimes, the Bellamy Brothers and the Charlie Daniels band.

Mr Obama has the opposite problem. After being damaged by Republican attack adverts this summer portraying him as the “biggest celebrity in the world”, he is seeking to dim the the aura of an A-list fan-club that includes many of “Hollywood liberals” so often decried by America’s conservative media.

Oprah Winfrey, the Queen of daytime TV who campaigned actively for Mr Obama during the primaries, will attend the Denver convention but has dismissed reports that she might take the stage with him. Her friend, Gayle King, said: “She thinks this is his moment.” George Clooney is also expected to be present and will host a lucrative fund-raiser for Mr Obama in Switzerland next month. Last week, however, the actor was forced to deny reports that they were in regular contact with the candidate through emails and text messages, offering “a million dollars to anyone who could prove” he had been. Indeed, he has said that campaigning for a man he once described as a “rock star” might end up doing more harm than good.

Others who are reported to have credentials for Denver include singers Madonna, Kanye West, Willie Nelson, Melissa Etheridge, Cyndi Lauper, Rufus Wainwright and the band, the Black Eyed Peas; actors Scarlett Johansson, Susan Sarandon, Gywneth Paltrow, Matt Damon, Ben Affleck and Matt Damon; as well as directors Spike Lee and Quentin Tarantino.

But Mr Obama’s team hope that such stellar power will not distract from the more grounded image they intend to project next week where his exotic international and inter-racial roots will be re-packaged as a very “American journey” that has enabled him to have a “deep understanding of what American families face”.

With polls suggesting many voters have reservations about his “otherness”, Mr Obama’s wife, Michelle, will open the convention with a prime time speech telling voters about the man she married and their relatively humdrum family life. Throughout the four nights there will be testimonials from family members and friends that emphasise his mother’s upbringing in Kansas, his grandfather’s service in World War II and his commitment to Christianity.

When he delivers his speech at the 78,000 seat Invesco sports stadium on the last night of the convention, Mr Obama will stand in the middle of the pitch surrounded by people from diverse American backgrounds whom he has met throughout the campaign. A film has been commissioned, part of which was recorded in wild western setting of Butte, Montana, that is designed to associate Mr Obama with all kinds of “Americana”.

The Republican convention, meanwhile, may be bailed out by the independent but liberal-leaning Creative Coalition which is bringing a lobbying delegation to St Paul that is expected to include actors Tim Daly and Kerry Washington, as well as producer, Tom Fontana. Ms Washington has already made her sympathies clear by appearing in a glitzy video for Mr Obama.

Robin Bronk, the director of the coalition, said the Republicans were keen to use Hollywood and show business to reach a wider spectrum of voters. “I think it’s a generational thing with McCain,” he said. “When the extent of diversity is how old all the white men on your ticket are, it doesn’t make for four compelling days of political conversation.”

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