“Bloomberg’s contribution appears to rely on the campaign finance loophole allowing campaigns to transfer unlimited funds to party committees in an election year.
As an individual, Bloomberg is only allowed to contribute approximately $35,000 a year to the DNC. But he can transfer unlimited money to his own campaign, which in turn can transfer an unlimited amount of funding to the party.”
https://www.yahoo.com/gma/bloomberg-transfer-18-million-national-democrats-2020-battleground-150000558.html