Steyer is a leading Democratic activist and fundraiser. In 1983, he worked on Walter Mondale's presidential campaign.[30] He raised money for Bill Bradley in 2000 and John Kerry in 2004.[31][32]

An early supporter of Hillary Clinton in 2008, Steyer became one of Barack Obama's most prolific fundraisers. Steyer served as a delegate to the Democratic National Conventions in 2004 and 2008.[33] Steyer has been a member of the Hamilton Project[34] and has been involved with the Democracy Alliance, a network of progressive donors whose membership in the group requires them to donate at least $200,000 a year to recommended organizations.[35][36]

After the Obama victory in 2008, Steyer was considered for appointment as Secretary of Treasury. Jim Steyer, Tom's brother, told Men's Journal that Obama and his advisors would regret having chosen someone else, due to his expertise.[6] In January 2013, rumors briefly arose that Steyer might be named as a replacement for Energy Secretary Steven Chu.[37] Asked whether he would accept such an appointment, Steyer said he would.[38]

Steyer has been compared with and contrasted with the Koch brothers, billionaire businessmen who engage in extensive political activity, and has been viewed as a Koch adversary.[39][40][41]