So I've been doing some reading about the 1928 election and wanted to put out my radical suggestion, that 1928 was the most important election in 20th century American history, despite being widely overlooked.
Prior to 1928 the vote of white ethnic voters (i.e. at the time- Italians, Irish, etc) was largely split between the major parties. Southern hostility towards Catholicism had largely prevented the incorporation of ethnic demands into the party platform and the ideological differences in the early 20th century were negligible (remember the progressive movement found its home in the GOP largely. By contemporary standards the GOP ran to the left of the Democrats in 1904 and 1916, were similar depending on the issues in 1908, and ran splinter candidates to the left in 1912 and 1924. Only in 1920 could you really posit a united GOP to the right of the Democrats in presidential politics). Furthermore, urban centers favored the Republican Party by a significant margin in 1924.
However, the 1928 nomination of Al Smith lead to a massive realignment. Catholic voters favored the Democrats in this election by a 75%-80% margin and major urban areas, as a result, swung heavily into the Democratic column. At the same time the Solid South splintered, the border states being lost and several deep South states (Alabama, Georgia) nearly joined them. While the South would return to the fold, it would never again be truly comfortable with Democratic presidents and would nominate splinter candidates or go at least in portion to the Republicans time and time again until finally fleeing the Democrats for good.
This was, in turn, incredible influential over the 1932 nomination process. The influx of ethnic, urban, and left-wing northerners into the party after 1928 tipped the balance of a narrow convention in favor of Roosevelt. If Smith had decided against running in this clearly lost-cause election and the Democrats had nominated say Cordell Hunt or James Reed, FDR would never have been able to get the 2/3 necessary to win the nomination in '32. The result would either have been John Nance Garner or, more likely, a compromise candidate of some sort.
So without Al Smith's nomination 1928, the national Democratic Party remains much more under the influence of the south, the New Deal may never come about, urban centers would not be near-universally Democratic, and progressivism remains divided between the parties.
I'm thinking of expanding from this scenario (although it would take an earlier PoD to deny Smith the nomination) but I was wondering for now what everyone else thinks. What do you think the most important election of the 20th century was? Bonus points for interesting choices
