Not that popular vote decides the outcome, but Nixon received 17,995,488 more votes than his opponent, which is the American record.
Second was Reagan in 1984 (16,878,120 votes), followed by Lyndon B. Johnson in 1964 (15,951,287 votes).
Too bad we will never see that again
Lyndon B. Johnson in 1964 (15,951,287 votes).
For only the second time a dem presidential candidate carried South Dakota