Seas of ink have been spilled on the subject of the marginality of the American left. But Michael Moore is anything but marginal. He has gained a level of household recognition that Noam Chomsky and Howard Zinn can only dream of. By playing a skilful double game – straddling the political and pop culture arenas – Moore has evolved into an instantly recognisable brand, much like Martha Stewart and Oprah Winfrey. The same can be said of no other left-wing activist in the world.