Vice President Kamala Harris and former President Donald Trump have so far not disclosed their top campaign fundraisers, also known as bundlers, ahead of the November election.

Though bundler disclosure is not required under federal law, transparency advocates have long pressed candidates to release information on their bundlers — typically wealthy and well-connected people who help solicit donations for campaigns. The practice has been around for decades, though it became more organized in 2000 upon then-candidate George W. Bush launching his “Bush Pioneer” donor program — giving supporters nicknames such as “Bush Rangers” and “Super Rangers.”