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How to Tell if 2016 is a Wave Election

With Hillary Clinton taking a large lead in the polls following the Democratic National Convention, journalists have begun to discuss the extent to which Democrats may be able to capitalize on these gains in down ballot races for the House and Senate. As has been the case in every recent election cycle, some journalists have even begun to write about whether or not 2016 could be a wave election.

Given the popularity of this concept among journalists and elections experts, being able to classify elections as either a “wave” or “not a wave” would appear useful. 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.

What exactly do I mean by “significantly affect the political status quo?” Past wave elections — at least those almost everyone agrees are waves — have produced some sort of policy upheaval, either through the passage of consequential new policy (e.g. the Affordable Care Act after 2008), or by blocking policy (e.g. the virtual halt in legislative action on President Obama’s priorities after 2010). If the party gaining seats in the election either wins a majority or exceeds the average number of seats it held over the course of the previous decade, then the seat gain is considered substantial enough — at least potentially —  to affect policy in a meaningful way.

As for the “substantial increase in seats for that party” portion of my definition, the seat gain for a party must exceed the average seat increase for the gaining party in the previous decade’s elections.[1] Measuring seat gains based on recent elections accounts for differences in electoral volatility over time and allows this definition to be applied to any political era. Some political observers were shocked by the double-digit seat gains in the House in 2006, 2008, and 2010 elections after the electoral stability of the early 2000s, but the late 1800s frequently featured double-digit seat swings. Indeed, even with a smaller House of Representatives, all but three elections from 1862 to 1898 saw one of the major parties gain or lose at least 20 seats.

One additional condition for this portion of my definition should be added based upon an observation made by political scientist Angus Campbell in his 1960 article, “Surge and Decline: A Study of Electoral Change.” In this article, Campbell notes that a “surge” in congressional seats by the president’s party in presidential election years is often followed by a natural “decline” in midterm years. Similarly, political scientists Bruce Oppenheimer, James Stimson, and Richard Waterman note in their 1986 publication, “Interpreting U.S. Congressional Elections: The Exposure Thesis” that congressional parties tend to lose seats in Congress when they are “exposed” — that is, have more seats than is typical for the party in that time period.

To account for the fact that the seat swing in a congressional election is linked to the seat swing in the election that preceded it, my definition requires that the seat swing in a congressional election must exceed any gains for the other party in the previous election. For example, while the Democratic Party gained 26 seats in the 1982 midterm election, this seat gain did not exceed the 34 seats Republicans gained in the previous election — and thus 1982 is not classified as a wave election under my definition.

When determining whether a Senate election is a wave election, I make one minor tweak to account for the fact that Senate elections are staggered. When calculating whether a Senate election is a wave, I use an average of the seat gain in the previous election and the previous time that Senate class faced the voters (six years prior).

If — and only if — an election satisfies both parts of my definition does that election then get classified as a wave election.

So what does this definition mean for 2016? First, for the House of Representatives, Democrats must gain at least 28 seats if this election is to be classified as a Democratic wave in the House. To satisfy the first part of my definition pertaining to “potential to significantly affect the political status quo,” Democrats would have to reach at least 215 seats (a net gain of 27 seats) based upon their average level of seats following the previous decade of congressional elections. And to satisfy the second part of the definition, Democrats would need to gain 28 seats in order to exceed the average net partisan gain over the previous decade. As an election needs to meet both parts of my definition in order to be counted as a wave, Democrats would have to gain at least 28 seats in order for 2016 to be counted as a wave.

This seat gain would put Democrats two seats short of a majority, but would create difficult circumstances for Speaker Paul Ryan as near-unanimous cooperation in the Republican caucus would be necessary in order to pass legislation opposed by Democrats. Given the recalcitrance of members of the House Freedom Caucus on a number of votes in recent years (including the vote for Speaker of the House), Speaker Ryan would probably have to rely on some Democratic votes to pass legislation.[2] It is also theoretically possible that Democrats would be able to find a few party-switchers before the House convenes in early January.

As for the Senate, Democrats would need to gain at least eight seats for this election to be classified as a Democratic wave in that chamber. The first part of my definition minimally requires Democrats to win the majority by gaining four seats (or five seats if Mike Pence becomes vice president), while the second part of my definition requires an eight-seat gain so as to exceed the average gain of the GOP in 2010 and 2014 where Republicans gained an average of 7.5 seats (six seats in 2010 and nine seats in 2014).[3]

Although large Democratic seat gains may not materialize in the House or the Senate in 2016, this definition provides a consistent method for determining whether an election is a wave, yet one that is flexible enough to be applied to elections in different political eras. Using this definition, all those who follow elections can better understand the magnitude of electoral volatility in a specific election.

Jacob Smith is a Ph.D. Candidate in the Political Science Department at the University of North Carolina-Chapel Hill, where he studies congressional elections, Congress, and public policy. He is especially interested in examining how political behavior and political institutions affect one another. He first constructed a definition for wave elections as part of his senior thesis at Kenyon College.


1. For example, Republicans gained 13 seats in 2014, so a value of 13 is used in the average for this election.

2. The GOP would also have to gain 28 seats for this election to count as a Republican wave under my definition, which seems unlikely given current electoral conditions and the large House majority Republicans possess.

3. Again, as a near impossibility since November is almost certain to yield GOP losses in the Senate, Republicans would need to gain at least seven seats in order for 2016 to be considered a GOP Senate wave under my definition.