When a committee (a person or group of people who receive or spend money for the purpose of influencing voters to support or oppose candidates or ballot measures) raises at least $1 million, it must report its top 10 contributors to the California Fair Political Practices Commission (FPPC). The committee must update the list when there is any change.
These lists are available on the FPPC website at http://www.fppc.ca.gov/transparency/top-contributors.html.
To research campaign contributions for candidates or ballot measures, visit the Secretary of State's website at powersearch.sos.ca.gov.