3. Share of primary votes: Share of primary votes during the primary elections is a way to judge outcomes of presidential elections.
Since presidential primaries began in 1912, only four incumbents have lost re-election, all garnering 72.8 percent of the primary vote or less. Herbert Hoover lost in 1932 after earning 36.0 percent in the Republican primaries, Gerald Ford lost in 1976 after earning 53.3 percent, Jimmy Carter (a Democratic incumbent) lost in 1980 after earning 51.1 percent, and George H.W. Bush lost in 1992 after earning 72.8 percent.
The most dominant Republican landslide re-elections in this time frame were won by Dwight Eisenhower (1956, 85.9 percent primary share), Richard Nixon (1972, 86.9 percent) and Ronald Reagan (1984, 98.8 percent). Trump won 94.0 percent in 2020.
In contrast, Joe Biden was trounced in the 2020 Democratic primaries in Iowa, New Hampshire and Nevada — the traditional indicators of general election viability. His running mate, Kamala Harris, dropped out before primary voting even began.