53% is on the brink of a landslide with a polarized electorate. That is about what Obama got in 2008. 39% is the worst that any incumbent President (Hoover) has gotten in a century, and that is 2% less than what Carter got in 1980 -- in an election in which the opposition is largely on the other side of the spectrum. (I am not counting the three-way election with the elder Bush).
To be sure, such a divide tends to swing ineffectively toward the eventual loser because in this case most of those in neither 'definitely' category are on the Right side of the political spectrum. But even a 6-2 split in favor of President Trump gives a 55-45 split of the electorate. Nobody has gotten more than 53.37% of the popular vote since 1984 in the Reagan blowout landslide that netted him 49 of 50 states.
(my favorite political map)
gray -- did not vote in 1952 or 1956
white -- Eisenhower twice, Obama twice
deep blue -- Republican all four elections
light blue -- Republican all but 2012 (I assume that greater Omaha went for Ike twice)
light green -- Eisenhower once, Stevenson once, Obama never
dark green -- Stevenson twice, Obama never
pink -- Stevenson twice, Obama once
No state voted Democratic all four times, so no state is in deep red.
In any event (electoral votes are for 2012, 2016, and 2020) we can see what 53% of the popular vote gets for a Democrat (Obama 2008 is the best approximation) and a general idea (Eisenhower 1956) of what as 14% split in the popular vote would look like. To be sure America is not what it was in the 1950s, as some constituencies (highly-educated people, most obviously) have expanded greatly and changed their ethnic composition, blacks vote much more, and of course the Hispanic electorate is much larger.
Figuring that the overlay between Obama 2012 and Eisenhower elections is such that despite getting 332 electoral votes in 2012, many of the political cultures that went for Eisenhower also went for Obama. How else can one explain Virginia going R for the first time in 24 years for Eisenhower (and D for the first time in 44 years for Obama), and the difficult trio of Massachusetts, Minnesota, and Rhode Island going for Eisenhower -- twice? I am guessing that Eisenhower did unusually well for the time with the usually-Democratic vote of white Catholics.
I see Obama and Eisenhower as similar in probity and competence. I also recognize that the Eisenhower/Rockefeller Republicans were always incompatible with Southern racist agrarian types and could never form a coalition except in the 1970s and 1980s as the Parties changed in regional and demograqphic orientation. Both Eisenhower and Obama did extremely well with people with college degrees, which suggests some similarities of style.
