That's a very fair assessment.
I would say that a "landslide" victory would any candidate getting between 55% and 60%+ of the popular vote. So, only a few historical landslides:
pre-1900: Mostly Washington, Jefferson, Madison, etc.
1904: T. Roosevelt (56.4%)
1920: Harding (60.3%)
1928: Hoover (58.2%)
1932: F. Roosevelt (57.4%)
1936: F. Roosevelt (60.8%)
1952: Eisenhower (55.2%)
1956: Eisenhower (57.4%)
1964: Johnson (61.1%)
1972: Nixon (60.7%)
1984: Reagan (58.8%)
Agreed.
While I don't have any official 'benchmark' as how to categorize landslides (I look at it on a case-by-case basis) I would agree with most of those.
Poll
