Who is winning the money race?

Democratic candidates have raised $100m (£49.3m) more than Republican rivals, proof of an enthusiasm gap that could determine the outcome of the 2008 election.

Why is it called the “money primary”?

Fundraising is the first test of a candidate’s popularity. The Clintons were seen as the best of their generation until Barack Obama raised $10m more than Hillary Clinton, even though he trails her in the polls. He has attracted 258,000 donors.

How much can individuals give?

A maximum of $4,600 (£2,267) – $2,300 for the primary campaign and $2,300 if the candidate is nominated for president.

So why do candidates court the wealthy?

It’s who you know, not how much you can give. The super-rich have the most hangers-on who want to impress them by supporting their candidate. Billionaires such as Ronald Perelman, the Revlon boss, will have a fat address book and can throw their homes open to hundreds of guests willing to pay to meet a future president.

What are bundlers?

They are supporters who can “bundle” small donations into million-dollar funds by getting friends, workmates and anybody they can think of to cough up. They are rewarded with phone calls, dinner and signed photographs with the candidate. Clinton calls her top 200 fundraisers “Hillraisers”.

What happens if a candidate runs out of funds?

John McCain, a former Republican frontrunner, allowed his campaign to run through $20m. He is considering taking federal matching funds to keep his candidacy alive - but if he does he will face strict limits on what he can spend.

Does a private income help?

Yes. Mitt Romney, the former governor of Massachusetts, has dipped into his fortune to stay in the top tier of Republican candidates. Money will also be no object for Michael Bloomberg, the billionaire mayor of New York, should he run as an independent.

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