Endorsed by the “Surprise Party”, she wooed the public with hundreds of radio and TV appearances, and, most famously, a 30-stop train journey from Hollywood to Omaha. Her name was Gracie Allen — an Irish-Catholic folk-dancer, famous at the time for a comic double act with her husband, George Burns. “It’s in the bag!” was Gracie’s farcically overconfident election slogan.

She wasn’t the first or the last comedian to pull such a stunt: Eddie Cantor and Will Rogers both ran in the 1930s, and Pat Paulsen did it five times between 1968 and 1996. Nevertheless, the Surprise Party campaign of 1940 was quietly subversive. On the subject of what role America’s “First Husband” would play if she became President, Gracie deadpanned: “There’s no job for George, because I don’t think it’s dignified for the President’s husband to work. People would be whispering that I can’t support him.”

I mention all this because the role of comedy and politics has never been under such scrutiny in the US — a fact that Hollywood has belatedly caught on to with Man of the Year, a movie starring Robin Williams as, yes, a comedian who runs for the presidency. The film opened this weekend to unamused reviews (“longer than the FDR Administration, less funny than Calvin Coolidge and deader than Abe Lincoln”, concluded the New York Post), but still managed to provoke yet another debate over whether voters trust America’s new breed of satirists more than they do the news itself, or the politicians in the news.

This may seem like a strange argument in Britain, where political satire has been mass-media entertainment since the Private Eye boom of the 1960s. But in the US the ridiculing of public figures has been largely confined to tame Saturday Night Live skits, Spy magazine (now defunct), cartoons and studiously inoffensive one-liners on the late-night talk shows. This is perhaps only to be expected from a superpower at the height of, well, its superpower.

But the American mainstream is changing, and the pundits are blaming one man: Jon Stewart, a 43-year-old Jewish comedian from New Jersey, who hosts The Daily Show, a nightly broadcast on the Comedy Central cable TV channel and seen in the UK on More4.

The Daily Show bills itself as “The Most Trusted Name in Fake News” (a play on CNN’s self-congratulatory slogan) and can best be described as a cross between Chris Morris’s The Day Today (or his Brass Eye series) and Have I Got News For You. Stewart is simultaneously smug, brainy, dumb and brilliantly spot-on, ridiculing the kind of minutiae that you would have to scour The Washington Post long and hard to find.

The result is that more 18 to 34-year-old male viewers now watch Stewart than any of America’s other evening news broadcasts. What’s more, The Daily Show’s audience has risen by 10 to 15 per cent every year during the Bush Administration, and now stands at about 1.5 million — huge for cable TV.

The Daily Show has even inspired a spin-off, The Colbert Report, hosted by Stephen Colbert, a “fake” rightwing news anchor, who was surprisingly invited to speak at this year’s White House Correspondents’ Association dinner, attended by George W. Bush. “I stand by this man because he stands for things,” said Colbert. “Not only for things, he stands on things. Things like aircraft carriers . . . and recently flooded city squares.” The speech was greeted with near-silence, but became an overnight YouTube hit. T-shirts bearing the slogan “Stewart/Colbert ’08” are now sold across the US, and Colbert’s speech became the No 1 download on iTunes.

But what are the long-term implications of all this? Will the Americans soon become as sardonic and irreverent as the British? What will happen when the US dumps its reserves of earnestness on to the open market? Is it even a good thing if the world’s only superpower suddenly becomes fashionably detached and self-aware? Perhaps, as Britain discovered in the early Nineties, the popularity of satire is inversely linked to the popularity of the government.

Or perhaps something more profound is going on. I get the sense, as I do when reading back Gracie Allen’s clever gibe about sexual inequality, that the balance of power is shifting; that innocence is being lost.

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