What Is a Wave Election, Anyway?

Democrats look poised to have a good showing on Tuesday.  They are almost certain to gain seats in the House, and may break even in a Senate cycle where they have to defend 10 seats in states Donald Trump won.  They’ll also add a number of governorships to their tally, along with a slew of state legislative seats.

But will it be a wave election?  This concept is something that analysts refer to routinely, but there’s no generally accepted definition of it.  We know that it is a really bad election for one party, but sometimes the lines become difficult to trace.  Everyone agrees, for example, that 2010 and 1938 represent wave elections, however that is defined. But what about years like 2006 or 1982, where the shifts were less dramatic, or even internally contradictory (in 1982, Republicans gained Senate seats despite losses in the House).

In a way, the concept of a wave is irrelevant.  Years like 1954, where Democrats barely gained seats but still flipped the House, are probably more consequential than a major wave year like 1922, where Democrats gained over 70 seats but failed to capture the chamber.  Whether 1982 is a wave election is irrelevant, as Democrats gained enough House seats to stop Ronald Reagan’s domestic agenda.

Yet waves still capture our imagination, in part because we tend to interpret them as nullifying a presidential mandate.  So the 1994 GOP wave forced Bill Clinton to declare that the era of big government was over (however temporarily) while the wave of 1966 stalled the Great Society.  In a presidential year, waves can be seen as inaugurating new eras, such as Barack Obama’s win in 2008 or Ronald Reagan’s in 1980.

So, we start with a definition: A wave election represents a sharp, unusually large shift in the national balance of power, across multiple levels of government.  To measure this, I turn to a metric devised by David Byler and me, which measures the power that a party has in the government at a particular point in time.  It’s a combination of the party’s share of the presidential popular vote, Electoral College, the House popular vote and seats in Congress, the makeup of the Senate, the makeup of governorships and the makeup of state legislatures.