A super PAC that has spent $2.8 million trying to get Jeff Brown elected mayor of Philadelphia has injected mystery into this year’s Democratic primary, with most of its funding coming from undisclosed “dark money” donors.

Brown, a grocery store operator and the only candidate who hasn’t held elected office, has so far been the greatest beneficiary of super PACs, outside spending groups that played a major role in the 2015 and 2019 mayoral races. A super PAC supporting Brown reported this week that it has raised more than $3 million.

And thanks to a loophole in campaign finance law, most of that money is coming from donors who can remain anonymous because their contributions were funneled to the super PAC through nonprofits. Three nonprofits donated $2,975,000 to For A Better Philadelphia, the super PAC supporting Brown, last year — accounting for 96% of the PAC’s fundraising in 2022 and 2023. But the donors to those nonprofits will remain unknown.

More than $2.4 million of that money came from a nonprofit registered with the Pennsylvania Department of State last year with the same name as the super PAC. The rest came from two established super PACs based in Washington. According to the city’s campaign finance law, nonprofits that fund super PACs trying to influence an election must file a report disclosing donors if the PAC spends $5,000 or more of that money within 50 days of the election.