Since 1944, all but one Democratic vice presidential nominees were sitting senators

[President Johnson]

Historical fun fact: Excluding sitting vice presidents renominated, all but one Democratic vice presidential nominees since 1944 were sitting US senators. The only exception is Geradine Ferraro, who ran as congresswoman in 1984. Sargent Shriver wasn't originally nominated in 1972, it was Thomas Eagleton, a Missouri senator, who was later dumped from the ticket. This is kinda amazing.

1944: Sen. Harry S. Truman (D-MO)
1948: Sen. Alben Barkley (D-KY)
1952: Sen. John Sparkman (D-AL)
1956: Sen. Eastes Kefauver (D-TN)
1960: Sen. Lyndon B. Johnson (D-TX)
1964: Sen. Hubert Humphrey (D-MN)
1968: Sen. Edmund Muskie (D-ME)
1972: Sen. Thomas Eagleton (D-MO) (replaced)
1976: Sen. Walter Mondale (D-MN)
1980: Vice Pres. Walter Mondale (D-MN)
1984: Rep. Geraldine Ferraro (D-NY)
1988: Sen. Lloyd Bentsen (D-TX)
1992: Sen. Al Gore (D-TN)
1996: Vice Pres. Al Gore (D-TN)
2000: Sen. Joseph Lieberman (D-CT)
2004: Sen. John Edwards (D-NC)
2008: Sen. Joe Biden (D-DE)
2012: Vice Pres. Joe Biden (D-DE)
2016: Sen. Tim Kaine (D-VA)
2020: Sen. Kamala Harris (D-CA)

[Battista Minola 1616]

Republicans have been much more varied:

6 incumbent Vice Presidents (1956, 1972, 1984, 1992, 2004, 2020)
5 Governors (1944, 1948, 1968, 2008, 2016)
3 Senators (1952, 1976, 1988)
2 Representatives (1964, 2012)
1 Ambassador to the United Nations (1960)
1 Former Director of the Central Intelligence (1980)
1 Former Secretary of Housing and Urban Development (1996)
1 Former Secretary of Defense (2000)