A single American citizen can donate a maximum of $3,300 directly to a presidential campaign. "White dudes for Harris" a video call with 190,000 participants is the latest in a series of collections with many small contributions.
For larger campaign donations, parties also drive "joint fundraising committees" where the rules are looser.
But there are also so-called political action committees or "pacs". What distinguishes a "super-pac" is that they are independent organizations that can receive and spend unlimited amounts of money on political campaigning.
On paper, a super-pac is not allowed to coordinate directly with a candidate.
But it's really questionable, says Karin Henriksson, journalist and USA expert.
Super-pac doubled Harris donations
The influence of money in politics has been a hot issue for a long time in the USA. In 2010, the Supreme Court repealed the rules that limited how much companies and trade unions could spend on political campaigns in a notable case. They considered it their right under freedom of speech.
Future Forward is currently the largest super-pac that directly supports Kamala Harris, according to the independent research institute Center for Responsive Politics.
On the same day that Harris' campaign fund collected a record-high $81 million, Future Forward received donation promises of almost double, $150 million.
It was certainly part of the pressure on Biden to leave, that the donations were so hesitant, says Henriksson.
The money gives access
Of the super-pacs that openly support Trump, Make America great again Inc is the largest. How much they collected after the assassination attempt on the ex-president has not been communicated. But on June 30, their total collected funds stood at $201 million, while Future Forward then stood at $134 million, according to the authority FEC, Federal Election Commission.
How much do the money influence the candidates and what is expected in return? It has always been the criticism of the entire system. Naturally, those who give a lot of money also get access to the candidate, says Dag Blanck.
Actor George Clooney has over the years organized large collections in Hollywood for the Democratic presidential candidates. In a notable opinion piece in The New York Times, days before Biden's withdrawal, Clooney described how Biden at their last meeting was not the same as before.
Then he has obviously had some access to the president, says Blanck.
Fairshake: $203 million (Super-pac that promotes cryptocurrency)
Make America great again Inc: $201 million (Republican for Donald Trump)
Senate majority pac: $167 million (Democratic for Senate elections)
Never back down Inc.: $146 million (Republican for Ron DeSantis)
Future Forward: $134 million (Is a so-called hybrid-pac, Democratic supporting Kamala Harris)
Source: Federal Election Commission, figures up to and including June.