Living Room Candidate
From the Museum of the Moving Image, "contains more than 300 commercials, from every presidential election since 1952, when Madison Avenue advertising executive Rosser Reeves convinced Dwight Eisenhower that short ads played during such popular TV programs as I Love Lucy would reach more voters than any other form of advertising. This innovation had a permanent effect on the way presidential campaigns are run."
Presidential Job Approval Ratings (via the Roper Center)
Compiles approval ratings from 5 polls. From Roosevelt to Obama.
U.S. Electoral College (via National Archives)
Presidential election vote totals and box scores back to 1789 along with details about how the college works.