2018 election analysis: Was 2018 a wave election?

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Updated 10:15 a.m. EST, December 28, 2018

This content is part of Ballotpedia's analysis of the 2018 midterm elections. For comprehensive election results, click here.

Was Election 2018 the blue wave that had been anticipated many months ago? By historical standards, no.

What Democrats needed in 2018
Election group	Seats needed for chamber/majority control	Seats needed for a wave election
U.S. House	D+23	D+48
U.S. Senate	D+2	D+7
Gubernatorial	D+10	D+7
State legislative	D+525	D+494

Begin with the U.S. House of Representatives.

In June, Ballotpedia analyzed every U.S. election going back to 1918 to find a baseline number for what defines a true wave washing over the party of an incumbent president.

The answer: The president’s party needs to lose at least 48 seats in the U.S. House. That’s the minimum number of seats lost in 11 of the 50 U.S. Congressional elections over the last century. Many elections in recent memory have met this threshold: Democrats lost 63 seats under President Obama in 2010 and 54 seats under President Clinton in 1994—the first midterm election for both presidents.

How did 2018 stack up?

Republicans began the evening with 235 seats. With one House race still too close to call as of December 3, 2018, Republicans were sitting on 200 declared victories and Democrats 234.

The Democratic Party gained control of the U.S. House but remained below historical wave levels.

The U.S. Senate wasn't even a close call.

The median number of seats lost in the Senate by the incumbent president’s party in every election going back 100 years is one. The average is two.

In 2018, Republicans expanded their majority to 53 declared seats, a gain of two chairs to their caucus room. If they were to have added more than two, that would have put them in the top 20 percent best performances over the last century.

What about state governments?

Now that’s something to talk about. Democrats had a good night taking over gubernatorial mansions, netting six new ones. The average loss of governors for the party of an incumbent president has been 2.66 per cycle, so Election 2018 was more than double the average.

Still, that didn't get it into the top 20 percent worst. President Obama in 2010 and President Reagan in 1982 each lost seven of their party’s governors during the first midterm election and then cruised to re-election. President Bill Clinton lost 10 governors in 1994.

In 1974, 5 Republican governors lost under President Ford's administration, just three months after President Nixon resigned due to Watergate.

Democrats also did not reach the wave threshold in state legislative elections, even though they captured 349 additional state legislative seats over the 2017-2018 election cycle (including 308 seats on election night). To reach a wave, they needed to win 494 additional seats.

See also

• 2018 election analysis: State government trifectas
• 2018 election analysis: Partisan balance of state legislative chambers
• 2018 election analysis: Incumbents defeated in state legislative elections
• 2018 election analysis: State legislative supermajorities
• 2018 election analysis: Partisan balance of governors
• 2018 election analysis: State government triplexes
• 2018 election analysis: Control of the U.S. House
• 2018 election analysis: Control of the U.S. Senate