Have the arts and politics ever been quite so entwined? This week, racist badinage by a group of F-list celebrities on British television ignited a full-scale diplomatic firestorm on the other side of the world. The Chancellor who would be king was left having to explain that Celebrity Big Brother is a rather grotty television programme and not a glimpse into Britain’s racist heart. Tony Blair indicated that he has no intention of stepping down before the summer, while The Trial of Tony Blair on Channel 4 simultaneously portrayed him in fiction, clinging to power and then hoist by his own hubris.

In France, inevitably, the merging of reality and art went a stage farther, when Nicolas Sarkozy, the presidential candidate, revealed that he has allowed the playwright Yasmina Reza to shadow his every moment in order to write an “existential portrait” of his soul, his hopes, dreams and everyday life.

Politics is not merely reflected, satirised and illuminated by art. Increasingly, politics and art — from pop culture to high theatre — are becoming indistinguishable. In some ways, we no longer believe the realities of politics until they are translated into art.

Reza’s book about Mr Sarkozy, the Interior Minister, is particularly extraordinary. Politicians have always recruited their own minstrels, artists to sing of their virtues and romanticise their lives. But this is something different. Reza, whose hit play Art earned about £140 million in theatres across the world, has been brought in as an independent artistic witness, a bard-on-the-wall. She has never met her subject, and Mr Sarkozy will have no control over the result.

Mr Sarkozy is a politician notorious for grooming his image; this sounds like a most foolish gamble, but it is not. He has plainly calculated that the French voting public will believe what Reza writes about him more than anything he says about himself. His action is a tacit admission that art can come closer to a persuasive truth than any amount of campaigning rhetoric or spun journalism. The play’s the thing. Or the novel. Or poem. Or painting.

The evidence of art superseding reality is everywhere. Joe Klein’s novel Primary Colors may stand as a testament to the character of Bill Clinton far longer than Mr Clinton’s own account of his presidency. When Mazarine Pingeot, the illegitimate daughter of François Mitterrand, sets out to depict her life, she does so in the form of fiction.

A televised biography of the Queen would doubtless be chewy and familiar fare, but the Queen as played by Helen Mirren is thrillingly weird and credible, a caricature that captures something authentic. We only believe when the truth is presented to us as drama, emotion, comedy or tragedy. Casual racism exists in every corner of Britain, but we only react to it as a reality when it is displayed in the unreal surroundings of the Big Brother house.

All this is both a reflection of an extraordinary artistic energy, but also a sign of how feeble and discredited politics has become. In totalitarian regimes, artists resort to allegory and satire to expose the truth, but the same is also true in a modern political world controlled by press release, leak and soundbite. Alastair Campbell cannot manipulate how he himself is portrayed, and so has become a staple figure in every modern political drama, from reconstructions of the Hutton inquiry and David Hare’s Stuff Happens, to In the Thick of It and The Queen.

Hare’s conception of his own role as a playwright was “to try to dramatise, more tellingly than any piece of reportage, what we took to be the irrevocable decline of our culture”. As the political culture has declined, so the audience for telling dramatisation has expanded.

We don’t believe the politicians. We tend to distrust the media. We view the lobbyists and pressure groups with deep scepticism. But we believe the artists. The sharpest critique of the political class comes not from within the system, but from outside, from the playwrights, novelists and artists.

Opponents of the war in Iraq have stopped marching and demonstrating. Instead, they watch the searing depiction of Guantanamo on stage, or revel in the squirming guilt of the Prime Minister played by Robert Lindsay in The Trial of Tony Blair. The Scott inquiry into the export of arms to Iraq, the death of David Kelly, the murder of Stephen Lawrence and the Bloody Sunday inquiry have all been made into compelling drama: the tribunal play has become a fixture of modern theatre.

Mark Wallinger’s new installation at Tate Britain, a vast reconstruction of the protest barricade that stood outside Westminster until police tore it down, is one of the strangest examples of art redefining reality. Brian Haw’s original protest, a collage of 600 tatty messages, posters, flags and banners, was endlessly photographed by Japanese tourists, but simply became part of the city landscape for everyone else. Now its peculiar contents will be scrutinised and analysed as a political artefact.

But that is what art does to politics: defining and simplifying, dramatising, mocking, exposing. Some artitistic reactions, such as Harold Pinter’s furious antiwar poems, are inspired in their anger. Some are merely cruel caricatures, like the grim pastiche of the David Blunkett story, A Very Social Secretary.

This may feel like a tawdry and lacklustre political age, but it may well prove to be a golden age of political art. Whether or not he becomes the next President of France, by bringing in a playwright to write his biography on the hoof, Mr Sarkozy has acknowledged the transcendent power of art over mere politics. The alchemy of the spin-doctor is nothing compared with the power of art.

Our own politicians should follow Mr Sarkozy’s lead. Gordon Brown should bring in Ken Loach as his writer-in-residence, right now. David Cameron should invite Nick Hornby to reveal his existential soul. Ming Campbell needs Tracey Emin to bring him to life. The battle of the artists: now that would be a real political contest.

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