The United States struggles with voter turnout, even during presidential election years. But low voter turnout is compounded during midterm elections that lack the wall-to-wall media coverage of a presidential campaign. Ever since the voting age was lowered to 18 in 1971, voter turnout at midterm elections has averaged 17 percentage points lower than presidential elections (presidential elections: 56.4 percent vs. midterm elections: 39.3 percent) [source: Skelley and Kondik].
Perhaps voter fatigue is partially to blame for the low turnout. Keep in mind that prior to this midterm election, there might have been primary elections held earlier in the year if two or more candidates from the same party were running for the same seat. Worse, there might also have been a runoff election a few months after the primary, depending on the state rules, if the top candidate didn't get more than 50 percent of the vote.
The 2014 midterm election registered the lowest voter turnout in a U.S. federal election since World War II [source: Montanaro]. Only 35.9 percent of eligible voters cast a ballot. The 2010 midterms, however, boasted the highest turnout in the previous 30 years at 41.0 percent, largely because of the Tea Party's success in rallying conservative opposition to President Barack Obama's policies [sources: McDonald, Skelley and Kondik].
Not only is voter turnout at midterm elections low, but different demographic groups are more or less likely to participate in midterm elections. In general, midterm voters are older, whiter and more educated on average than general election voters [source: Skelley and Kondik]. In recent decades, this has had political implications, since older, whiter, more educated voters have been more likely to vote for Republican candidates (although the more-educated demographic trended Democrat in the 2016 election).
Since 1978, Republican voters have been more likely to show up for midterms by an average of 3 percentage points. The Republican turnout advantage has been greatest during midterms when a Democratic president is in the White House. In three such midterm elections, Republican voter turnout was 6 percentage points higher than Democrats (1978, 1994, 2010) [source: Enten].
From exit poll data, it's clear that non-white voters continue to make up a smaller percentage of midterm voters compared with presidential elections. For example, in the 2008 presidential election, 26 percent of all voters identified as non-white, but in the 2010 midterms, that share was only 23 percent. The same 3-point drop occurred between the 2012 presidential election and the 2014 midterms. Since non-white voters are more likely to identify as Democrats, that's another midterm advantage for Republicans [source: Skelley and Kondik].
Even with historic imbalances in voter turnout, one trend has proved true in almost every midterm election in the past 50 years — the party that controls the White House gets pummeled. In the next section, we'll explore the so-called "midterm penalty" and other theories for midterm power transfers.