Back in 1984, when the election was a foregone conclusion and the pundits had lots of time to blather, a couple of them got into an argument over Reagan’s 59% of the popular vote really constituted a “landslide.” They felt 60% was the magic number. By that measurement, the only landslides in the last 100 years would be Harding (1920), Roosevelt (1936), Johnson (1964) and Nixon (1972). That’s about 15% of all the presidential elections of that period.
But it’s a lot easier to get 60% of the electoral vote than popular vote. The highest 15% of electoral vote percentages during those elections ranged from 91% (Reagan 1980) to 98% (Roosevelt 1936.)
So let’s say from an electoral vote standpoint you need 90% of 538 EV. That’s about 484.