Clerk of the U.S. House of Representatives: Election Statistics 
Official vote counts from 1920 to the present for presidential and congressional elections compiled by the Office of the Clerk of the U.S. House of Representatives. This site also contains links to election resources found on the websites of the Census Bureau, National Archives, Federal Election Commission, and state election offices.
Dave Leip's Atlas of U.S. Presidential Elections
This site provides national election results and maps for presidential elections from 1789 to the present, as well as state and county results for more recent elections. It also contains results for U.S. Senate and gubernatorial elections from 1990 to the present.
Every two years, the Federal Election Commission publishes Federal Elections, a compilation of the official, certified federal election results obtained from each state’s election office and other official sources. This page provide the primary, runoff, and general election results for the U.S. Senate, the U.S. House of Representatives and, when applicable, U.S. President from 1982 to the present.
National Archives: Historical Election Results
The Office of the Federal Register at the National Archives coordinates the functions of the Electoral College on behalf of the Archivist of the United States, the States, and the Congress. This site contains the electoral votes and popular votes from 1789 to the present.
A New Nation Votes: American Election Returns 1787-1825
A searchable collection of election returns from 1787 to 1825. The data were compiled by Philip Lampi. The American Antiquarian Society and Tufts University Digital Collections and Archives have mounted it online with funding from the National Endowment for the Humanities. The site contains federal and state election returns.
Official vote counts from 1920 to the present for presidential and congressional elections compiled by the Office of the Clerk of the U.S. House of Representatives.
Election Results: State
National Association of State Election Directors
The National Association of State Election Directors presents a roster of state election offices that contains links to official state Web sites. From this roster select a specific state to find official election results from recent elections. Election results provided on each site will vary depending on the state.
National Governors Association
The National Governors Assocation provides gubernatorial election results from 2009 to the present.
Election Studies and Data, Exit Polling, Voting and Registration
ANES: American National Election Studies
A collaboration of Stanford University and the University of Michigan, producing data on voting, public opinion, and political participation. The ANES produces high quality data from its own surveys on voting, public opinion, and political participation. Data are available in the form of raw data and statement files that can be run using statistical software such as SAS, SPSS or Stata. The help page
Center for American Women and Politics: Voters
The Center for American Women and Politics (CAWP), a unit of the Eagleton Institute of Politics at Rutgers, The State University of New Jersey, is nationally recognized as the leading source of scholarly research and current data about American women’s political participation. This site presents data and analysis of women's voting behavior, including statistics on turnout and the gender gap in voting.
This archive contains data on election results, voting behavior, and electoral politics. The core data for the archive are state, county and district level election returns for all recent state and federal elections.
The Roper Center for Public Opinion Research: U.S. Elections
The Roper Center provides primary, national, and state exit polling date for presidential elections from 1976 to the present. Membership
U.S. Census Bureau: Voting and Registration
Voting and Registration data have been collected biennially by the U.S. Census Bureau in the November Current Population Survey (CPS). The statistics presented on this website are based on replies to survey inquiries about whether individuals were registered and/or voted in specific national elections. For the purpose of these estimates, election types are considered to be either congressional or presidential.
United States Election Project: Voter Turnout
Dr. Michael McDonald, an Associate Professor at George Mason University, provides national and state voter turnout statistics from 1980 to the present.