American National Election Studies (ANES), 1948+ Oldest continuous series of survey data investigating electoral behavior and attitudes in the United States (since 1948). ANES interviews are conducted before and after presidential elections and after midterm Congressional elections (1958-2002). Post-election interviews include questions on actual voting behavior. Click on "Data Center" at the top of the page to download the datasets for the various waves. Click on "Utilities" to browse/search lists of questions and variables. For quick online exploration use Berkeley's SDA service; for trend tables, like party ID by various demographics, see the ANES Guide to Public Opinion and Electoral Behavior
Cooperative Election Study (CES), 2005 + Formerly known as the Cooperative Congressional Election Study (CCES), the CES is a 50,000+ person national stratified sample survey allowing analysis at the congressional district level. Half of the questionnaire consists of Common Content asked of all respondents (much of which remains the same each wave), and half of the questionnaire consists of Team Content designed by each participating team and asked of a subset of 1,000 people (generally not accessible). Topics include registration and voting, political knowledge, ideology, and policy preferences related to key issues on which Congress has taken roll call votes in the preceding two legislative sessions. Has both pre-election and post-election waves. Includes validated registration and turnout variables. An online analysis interface is available (registration required first)
General Social Survey (GSS), 1972+ The GSS is a long running survey of social, cultural and political indicators. Probably the single best source of data on societal trends. Includes questions on presidential vote choice, party ID, interest in politics, and more. You can download the full dataset or extracts, and you can also analyze it online using Berkeley's SDA service, which also has a Quick Tables feature to generate crosstabs of major trends, like party ID by demographics.
Pew Research Center, 1997+ The Pew Research Center is a "nonpartisan fact tank" conducts public opinion polling, demographic research, media content analysis, and other empirical social science research around several broad themes: U.S. politics and policy, use and influence of the media, the role of the internet and technology, Hispanics in the U.S., the role of religion in public life in the U.S. and beyond, social & demographic trends in the U.S., and global attitudes. All data and reports can be browsed by topic, searched by question, and are freely downloadable. 1997-present. Many recent surveys are based on their American Trends Panel, a nationally representative, random panel sample that allows for longitudinal analysis.