While simply massive and (potentially) a bit unwieldy, the Database on Ideology, Money in Politics, and Elections (DIME) is, quite literally, unparalleled in terms of scope. Indeed, the database contains over 100 million political contributions made by individuals and organizations to local, state, and federal elections spanning a period from 1979 to 2012.
DIME "is intended as a general resource for the study of campaign finance and ideology in American politics. The database was developed as part of the project on Ideology in the Political Marketplace, which is an on-going effort to conduct a comprehensive ideological mapping of political elites, interest groups, and donors using the common-space CFscore scaling methodology (Bonica 2013). Constructing the database required a large-scale effort to compile, clean, and process data on contribution records, candidate characteristics, and election outcomes from various sources. The resulting database contains over 100 million political contributions made by individuals and organizations to local, state, and federal elections spanning a period from 1979 to 2012. A corresponding database of candidates and committees provides additional information on state and federal elections."
Motivations for the database's creation include: "to make data on campaign finance and elections (1) more centralized and accessible, (2) easier to work with, and (3) more versatile in terms of the types of questions that can be addressed." Housed at Stanford University, the database website requires users wishing to access the data to establish an account (free of charge) and includes direct access to a codebook.