Why was the 1920 election such a landslide?

[TheReckoning]

Was Wilson really that unpopular? Why?

[darklordoftech]

People were convinced that Wilson’s terms for joining the League of Nations would obligate America to go to war again if another war broke out in Europe. Also, the economy was actually worse in 1920 than in 1929 (it was only in 1931 that it became the “Great Depression”), there was the Spanish Flu pandemic, and Wilson alienated Democratic-voting demographics with the Palmer Raids. It was said that if a dog was the GOP nominee, the dog would win. Wilson was as popular in 1920 as Herbert Hoover was in 1932.

[Podgy the Bear]

In addition to the terrible economy and Spanish flu pandemic (bad enough in themselves), here are other reasons for the biggest Republican landslide in history:

1) The reunification of the old guard and progressive Republicans which brought the majority party back together--probably close to 1908 levels, which in itself would have clinched an electoral college win.  The 1920 Republican convention could have split but they unified behind Warren Harding--whom nobody disliked.   

2) Wilson's alienation of just about everyone except the Democratic natural base of the South.  German-Americans created a massive backlash in the Midwest (Cox couldn't get 20 percent of the vote in MN, WI, and ND, states that Wilson barely lost/won in 1916).  And going against Irish post-war interests created huge majorities for the Republicans in NYC and Boston (something we'll never see again).

3) The Democrats had little money to fight a national election.  The Republicans were well funded.

[Orser67]

Darklordoftech and mollybecky both gave good answers. I'll add a few points. First, the Republicans were the sort of naturally dominant party between about 1896 and 1932 (sometimes known as the Fourth Party System), and 1920 was a reassertion of that dominance after Wilson's fluky victory in 1912 and his narrow re-election in 1916. Additionally, the 1920 presidential election represented what Harding called a "return to normalcy", not only from the Wilson administration but from the entire progressive era. In other words, many people were tired of the activist government of the Roosevelt, Taft, and Wilson administrations.

Also, I think it's important to understand the absolute sh**tshow that was the Wilson administration after the end of WW1. You simultaneously had high unemployment, high inflation, one of the worst pandemics in U.S. history, some of the worst racial unrest in U.S. history, the First Red Scare, labor unrest, a chaotic demobilization both of U.S. soldiers and more broadly of wartime organizations like the Railroad Administration, a polarizing fight over the League of Nations, and, in the midst of all this, the implementation of Prohibition. Any party likely would have been doomed by this confluence of factors, but the situation was made even worse after Wilson suffered a stroke in late 1919 that left him largely incapable of providing leadership.

[Southern Senator North Carolina Yankee]

To dive deeper into the demographic collapse for the Democrats, Wilson was an anglophile and that combined with war against Germany and alliance with the British Empire, meant that German voters were pissed, Irish voters were and of course this meant that a good chunk of the Northern Democratic base was thus pissed off.

To add to this you had the Red Scare and the Palmer raids and this would have alienated a lot of Eastern Europeans, Jewish voters and of course more far left voters who would have supported Wilson for his progressive agenda but now found themselves disgusted by the final result.

This left the Democrats with the South and they got wiped out everywhere else. Were it not for the South, it is very possible that the Democrats might have given way to a Socialist or Labor party as happened in the UK. The Liberals had similar problems of alienating their core supporters with war policies and then combined with the split in the party, allowed for the Labor Party to overtake them and that has not reversed itself since that time period.