However, Rove's short-term ploys have undermined long-term Republican possibilities. His polarising and paranoid politics have been an intrinsic aspect of Bush's consistently radical presidency, which may be checked and balanced for the first time with the election of the 110th Congress. Rove's legacy may be to leave the Republicans a regional southern party whose constrictive conservatism fosters a solid Democratic north.

Rove's dismissal of the very notion of a political centre was enabled by September 11, which provided him with dramatic material to stigmatise the opposition as dangerously soft and to turbo-charge inflammatory social issues such as gay marriage. By defending hearth and home from enemies at the door and behind closed doors, Rove maximised turnout of the galvanised hardcore.

Yet Rove did not achieve his ambition of a grand realignment of US politics. In Bush's second term Rove attempted to force privatisation of social security, but Bush's plan did not receive a single committee hearing in the Congress. Hurricane Katrina exposed the corrupt political swamp of his government. And Iraq corroded the thin mandate he had left.

Having set the theme of the midterm elections campaign as "staying the course" in Iraq, Bush declared a week ago that he had never uttered the phrase - which he had used dozens of times. None the less, on the stump he follows the Rove script of politicising terror, claiming the opposition is unwilling to defend the country and is un-American.

Though Bush has abandoned his "staying the course" slogan, Rove explains that the policy is clear and simple: "The real plan is this: Fight, beat 'em, win." His formulation is aimed less at the Shia-dominated government of Iraq, recalcitrant about disbanding murderous militias, than the disillusioned Republican base, especially white evangelicals, whose support in recent polls has fallen one-third since 2004.

Frantic Republicans are reduced to raising the spectres of racial and sexual panic. In Tennessee, where Harold Ford, an African-American, is running even with the Republicans, a Republican National Committee TV ad produced by a Rove protege features a blonde vixen beckoning in a sultry voice, "Call me, Harold." In Virginia, the former Reagan secretary of the navy turned Democratic candidate James Webb, who is also an acclaimed novelist, is being attacked for sexually explicit passages in his books - written decades ago, based on his experiences as a soldier in Vietnam.

It is conjectural but conceivable that had Bush governed after September 11 as he campaigned in 2000, as a "uniter, not a divider", he might have been able to forge a durable centre-right consensus. That would have required appointing prominent Democrats to his cabinet, reining in his power-mad vice-president and secretary of defence, making moderate court nominations, and listening to the voices of sceptical realism on invading Iraq. Imagining this parallel universe underscores how Rove's victories helped pave the way to losing the potential for a lasting majority.

Sidney Blumenthal will discuss his new book, How Bush Rules, at the Newsroom in London on November 15. For details see guardian.co.uk/eventsandoffers.

Guardian Unlimited © Guardian News and Media Limited 2006

###