Wikipedia
MapLight
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MapLight is a nonpartisan, nonprofit research organization that reveals and tracks the influence of money in politics in the United States. The organization publishes a free public database linking money and politics data sources, including campaign contributions to politicians, how politicians vote on bills, and support and opposition to legislation. MapLight provides data on both campaign finance and voting behavior in one database.
MapLight uses an in-house research team in addition to data sources that include the National Institute on Money in State Politics, the Center for Responsive Politics, and Govtrack.