Twenty Labour candidates are busy trying to get elected, and they're all going to need some cash.

Once you tot up those vying to be leader, deputy leader, London mayoral candidate, Scottish leader and Scottish deputy - there are a lot of hopefuls.

Who will pay for their offices, spokespeople and campaigns?

In the 2010 leadership fight David Miliband raised more than £300,000. But key funders last time may not spend a penny this year.

Sainsbury shuts up shop

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David Sainsbury gave David Miliband £138,000 in 2010. This time round his wallet - I'm told - will stay shut. As Chancellor of Cambridge University and chair of the board of the Institute for Government he's keeping out of the fight. That's despite giving over £100,000 in a single month this year to a campaigning organisation set up by David Miliband (Movement for Change) and the New Labour group Progress, whose vice chair is leadership contender Liz Kendall.

The unions

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Unite - which gave Ed Miliband £100,000 in 2010 - will choose who to back within a week, following a hustings event. They say the decision will not be made by general secretary Len McCluskey alone, but by a 60-strong committee. Sources at another big union - Unison - say they may well decide not to back any candidate. Unlike last time, unions won't have a one third say in choosing the leader.

The Donors

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So the candidates may have to rely on big Labour donors. One - John Mills (pictured) - confirms he has been approached, and is still making up his mind whether to support Andy Burnham, Liz Kendall or Yvette Cooper for the leadership. London mayoral hopeful Tessa Jowell is likely to get his backing though; she's his sister-in-law.

The Declarations

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Some candidates have already announced declarations. JK Rowling gave Tom Watson £4,000 for his deputy leadership campaign. The most recent data from the Electoral Commission shows advertising executive Trevor Beattie and former businessmen turned Labour ministers Paul Myners and Mervyn Davies have backed Jowell. It doesn't include any declarations for the leadership candidates. The money must be slow to roll in for them, because MPs have to report all donations over £1,500 to the Registrar of Members' Financial Interests within 28 days of accepting them. The information is then published by the Electoral Commission. We'll get a fuller picture when the new Register of Members Interests showing all MPs' donations goes online in July.

Please give generously

Image copyright Ross Hawkins

Of course politicians can always ask the public if they would like to give generously. Left-wing leadership contender Jeremy Corbyn is trying to fund his campaign through small donations. As his website shows, he's got a long way to go to match the big money donors of 2010.