Information on reported voting and registration by various demographic and socioeconomic characteristics is collected for the nation in November of Congressional and Presidential election years in the Current Population Survey (CPS). The CPS is a monthly survey of about 50,000 households conducted by the Bureau of the Census for the Bureau of Labor Statistics.
From website:"The American Presidency Project (americanpresidency.org), was established in 1999 as a collaboration between John T. Woolley and Gerhard Peters at the University of California, Santa Barbara. Our archives contain 105,368 documents related to the study of the Presidency."
The Gallup Poll News Service is the internet's leading polling-based news source. The Gallup Poll News Service provides news centered on public opinion. Published each business day, articles from the Gallup Poll News Service analyze findings and trends in politics, business, social issues, and Americans'lifestyles. From 2003.