Extremely unconventional woman returns to upstage the conventions

She won't be marching in the streets. She won't be calling for the overthrow of capitalism and of corporate control of the global economy (although she might be tempted). Nevertheless, if anyone is going to shake the over-rehearsed stiltedness out of this summer's American political conventions and capture the imagination of those for whom the whole circus is supposedly intended - the voters - then Arianna Huffington is surely the woman for the job.

She won't be marching in the streets. She won't be calling for the overthrow of capitalism and of corporate control of the global economy (although she might be tempted). Nevertheless, if anyone is going to shake the over-rehearsed stiltedness out of this summer's American political conventions and capture the imagination of those for whom the whole circus is supposedly intended - the voters - then Arianna Huffington is surely the woman for the job.

Witty, shamelessly contrary and eternally combative, Arianna - as she is universally known - is the driving force behind the Shadow Conventions that will stalk the mainstream politicians, both in Philadelphia where the Republicans will anoint George W Bush as their presidential candidate next week, and in Los Angeles where the Democrats are gathering in mid-August for the coronation of Al Gore.

Count on her to keep things lively (the title of her latest book is How to Overthrow The Government); count on her to keep the celebrity count high (among the speakers she has attracted, Gore Vidal, Warren Beatty and Mr Bush's erstwhile challenger, John McCain); but, above all, count on her to stir the pot by focusing on issues she believes the two big parties would rather avoid.Her subjects will include the growing disparity between rich and poor and the myths of America's much-touted "prosperity", the corruption of political campaign financing that enables corporations to subvert the public interest through money, and the moral and political bankruptcy of the so-called War on Drugs, whereby addicts are criminalised and public funds are squandered on prison-building rather than education and rehabilitation.

It is hard to know how to define Arianna. Newspaper columnist, political salonkeeper, television personality - none really does justice to her larger-than-life presence. But what she does have is attitude.

She has been many things to many people in her career: president of the Cambridge Union, anti-feminist, bestselling biographer of Picasso, and (in her least convincing role) dutiful political wife. She was considered Republican until she made clear she had no respect for any political party, a conservative until the Shadow Conventions filled her with a radical zeal reminiscent of the counter-culture of the Vietnam War era, and a shameless élitist until she unexpectedly became an advocate for the poor.

After divorcing her Republican husband, Michael, in 1996 she became a political ally of the former House speaker, Newt Gingrich - architect of the Republicans' controversial "Contract with America" - but had the courage to drop him when he became an embarrassment. From then on, her drift to the left became a surge, and now, as she threatens to upstage the mainstream parties, the politicians are getting nervous.