"Double flips" have become rare in Senate midterms

Number of seats changing party caucuses in midterms since World War II, and net gain

Note: Flips reflect changes in Senate caucus control, not merely party labels; independents and minor-party senators are assigned to the major-party caucus they joined. Minnesota in 2002 is counted as D-to-R despite a last-minute caretaker appointment; New Hampshire’s 1975 re-vote (!) is assigned to the disputed 1974 election. Newly created Alaska and Hawaii seats are excluded once those territories became states.