US election: Guide to the battle

In US congressional elections the winner is "almost always" the candidate who has raised the most money, according to the Center for Responsive Politics.

FUNDS AT 15 OCTOBER 2008 Where the rivals get their cash

In presidential elections since the 1970s, candidates have had the same amount of cash at their disposal in the crucial final weeks of the election, because they have all accepted federal funding.

This year, Barack Obama has rejected federal funding and a record-breaking fundraising operation has given him a huge financial advantage.

The Obama campaign had raised $660m by 15 October, after raking in an unprecedented $150m in September alone. It had $66m still to spend, plus any funds raised in the second half of October.

John McCain had $25m left to spend before 4 November, out of his $84m of federal funds. His campaign had spent a total of $292m by mid-October.

However, the national party committees are also able to raise funds, and the Republican National Committee (RNC) has outstripped the Democratic National Committee (DNC), slightly narrowing the funding gap.

By mid-October, the DNC had raised $206m, and the RNC $328m. However there are some restrictions on how this money may be spent.