When one political party makes major gains in the United States House and Senate and the other has few losses.
Mark Barabak: “There is no authoritative definition of a wave election. (Which is not to be confused with a realigning election, like those in 1932 and 1968, in which a party forges a new and enduring presidential coalition.) A wave election is commonly considered one in which a political party wins a large and lopsided number of House and Senate seats while sustaining minimal losses.”
“In the past 20 years, there have been several wave elections of that type, including 1994 when Republicans netted 54 House and 10 Senate seats; 2006 when Democrats won 31 House and six Senate seats; 2008 when Democrats gained 21 House and eight Senate seats, and—most spectacularly—the last midterm vote, in 2010, when the GOP won 63 House seats and four in the Senate.”
Jacob Smith: “Unfortunately — and surprisingly given the widespread use of this term — there is not a precise definition of this concept. To try to correct this, I have developed my own definition that combines both scholarly rigor with the basic intuition of a wave election being a ‘big win’ for one side at the expense of the other.”
“Specifically, I define a ‘wave election’ to be a congressional election that (1) produces the potential for a political party to significantly affect the political status quo as (2) the result of a substantial increase in seats for that party.”
Charlie Cook says wave elections are usually the result of a “overarching, nationwide dynamic.”