For the first hundred years of the competition between the Democratic party and the Whigs and the Republicans, no president was reelected with more than 56% of the popular vote. . . .
Then we see a [steep] increase in presidents’ reelection percentages. Franklin Roosevelt is elected to a second term in 1936 with 61% of the popular vote. Dwight Eisenhower wins a second term in 1956 with 57%. Lyndon Johnson wins a full term with 61% (pre-assassination polling suggests John Kennedy would have done nearly that well had he lived). Richard Nixon wins a second term in 1972 with 61%. Ronald Reagan wins a second term in 1984 with 59%. . . .
Why? Because they were seen as having delivered both prosperity and peace. Voters who lived through the Depression of the 1930s and World War II in the 1940s knew what war and economic collapse could do. They understood the horrifying damage it inflicted on people’s lives and the things they held dearest. They were ready to cross party lines and reward presidents who seemed to protect them from such scourges.
As that generation of voters passed, Barone goes on to explain, American politics re-polarized.