By popular vote margin:
1. 1920 (26.2%)
2. 1924 (25.2%)
3. 1936 (24.3%)
4. 1972 (23.2%)
5. 1964 (22.6%)
6. 1904 (18.8%)
7. 1984 (18.2%)
8. 1932 (18.0%)
9. 1928 (17.4%)
10. 1956 (15.4%)
But the highest % of the vote goes to Johnson's 1964 election (61.1%)
This. Although Johnson landsliding in the northeast and carrying the South despite the civil rights act was pretty badass. Also, Reagan nearly pulling off a clean sweep in '84, and getting David Horowitz and Peter Collier to vote for him was pretty swag, too.
