The candidates for the US presidency have been raising millions of dollars every month. Find out below who's ahead in the money race and where the cash is coming from.
FINANCIAL OVERVIEW as of 15 Oct 2008
Barack Obama has raised more money than John McCain partly because of the excitement generated by the Democratic nomination battle. His donors had pressing reasons to donate, from January right through to June, while Mr McCain wrapped up the Republican nomination in March.
Mr McCain has decided to take public financing, which means that from 1 September he has a maximum of $84m [£51m] to spend on his campaign. The McCain campaign is no longer accepting donations, except to its compliance fund - money to pay for lawyers, accountants and other expenses involved in maintaining compliance with federal election laws. The Republican National Committee, however, can still raise money to support the McCain campaign.
Barack Obama is the first candidate not to take public financing since the system was introduced in the mid-1970s. In September, the Obama campaign raised $153m [£93m], a new record for a single month, and can continue fundraising.
So far, the Republican National Committee's traditional strength at fundraising has given it a clear lead. The Democrats only managed to out-raise them for a single month, August, and the Republicans have almost four times as much in the bank.
There is a question about how effectively they will be able to use this huge cash advantage. Election rules state that, because John McCain has accepted public funding, the Republicans can only provide $19m of direct help to his campaign.
After this $19m, the money should only be used to get out their base through registering and motivating Republican voters. However, political parties are adept at finding loopholes in electoral guidelines, so they may still find ways to press their advantage.
A look at where the candidates are receiving most donations reveals that Barack Obama has a distinct advantage in heavily urbanised states such as New York, Illinois and California, while John McCain is receiving significant support from the key battleground state of Florida. The McCain campaign is weaker in the liberal North-east.
One area where the Obama campaign has broken the mould of US election finance is in making big efforts to attract small donors. As a result, before federal fundraising ended Mr McCain's appeal for donations, Mr Obama had raised four times as much as John McCain from donors contributing less than $200.
MAJOR DONORS as of 30 Sep 2008
Anyone making a donation above $200 must indicate their occupation. These figures can be combined with donations from unions, industry associations and political groups to give an idea of who is supporting each campaign.
John McCain is only significantly ahead on donations from retired people and from the oil and gas industries. In all almost every other area, Barack Obama is either on roughly level terms or ahead, even in those where the Republicans would expect to be strong, such as real estate, business and finance.
CAMPAIGN SPENDING as of 30 Sep 2008
The majority of a campaign's spending is split between media - the adverts, websites and leaflets that deliver the candidate's message - and administration, which includes offices, salaries and travel.
The biggest single expense is paid television advertising, which has been concentrated in the key battleground states.
The campaigns also reinvest a portion of their money on fundraising activities, such as live events and phoning supporters, to generate more donations.
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