Battleground USA: Where the presidency will be won and lost

This weekend, the race for presidency of the United States began in earnest. With the party conventions behind them, the two candidates – one a man who could become the oldest ever to enter the White House, the other who would be the first black president – have returned to the campaign trail with a vengeance. Barack Obama is visiting fairgrounds in Indiana; his Republican opponent, John McCain (plus running mate Sarah Palin), is in Colorado and New Mexico. Needless to say, the states are key ones.

They have 57 days to impress 150 million potential voters with their case. They will do it with shows of patriotism, as on 11 September when both will be at Ground Zero, New York. They will do it in the three debates, the first of which will be on domestic policy on 26 September. They will do it with speechifying across the union – inspiring, if theatrical, in Obama's case; stilted, yet homely, in McCain's.

And, incessantly, inescapably, they will do it in television ads, the budget for which in Obama's case is almost bottomless. And then, as America found in 2000, it could yet all come down on 4 November to just one state.

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