What We Know About the Midterm Elections in the United States

The map is biased against Democrats, but it wouldn’t take that much for a Democratic wave to turn into a tsunami.

View of the United States Capitol in Washington DC, August 4, 2013
View of the United States Capitol in Washington DC, August 4, 2013 (Jeffrey Zeldman)

The map is biased against Democrats, but don’t overestimate the Republican turnout advantage. It wouldn’t take that much for a Democratic wave to turn into a tsunami. White women and college graduates are likely to decide the outcome.

Here is what we know about the upcoming congressional elections in the United States.

The map is biased against Democrats

David Wasserman writes:

Even if Democrats were to win every single 2018 House and Senate race for seats representing places that Hillary Clinton won or that [Donald] Trump won by less than 3 percentage points — a pretty good midterm by historical standards — they could still fall short of the House majority and lose five Senate seats.

Partly this is due to bad timing: Democrats must defend 25 of their 48 Senate seats. Republicans need to defend just eight of their 52.

But partly this is also due to Republican gerrymandering and Democratic voters clustering in cities and coastal states.

Democratic wave could turn into a tsunami

The flip side of gerrymandering, Nate Silver points out, is that it doesn’t take all that much for the Democrats to go “from a ripple to a tsunami”.

It’s a pretty nonlinear effect once you start getting into the territory where supposedly safe gerrymandered seats come into play.

Democrats could win the popular vote by 6 percentage point nationwide and still not take the House. But add a few points and they suddenly gain dozens of seats.

Don’t overestimate the Republican turnout advantage

Republican voters were more likely to turn out in 2010 and 2014, but Harry Enten reports that this had more to do with Barack Obama being president than Republicans having a built-in advantage.

Historically, the Republican (GOP) turnout advantage is either exacerbated or all but canceled out depending on which party controls the White House.

With a Democrat in the White House, the GOP turnout advantage gets even bigger. With a Republican in the Oval Office, the GOP on average barely has any advantage at all.

White women and white college graduates could decide the outcome

Conservative columnist Matthew Continetti writes:

Both demographics broke for Trump in 2016. He won white women by 10 points and white college grads by 4 points.

But these are precisely the voters that have turned against him and his party.

If white women and college graduates continue to be repelled by the president in an off-year election where he is not on the ballot, then the GOP majority is finished.

Two factors argue in Republicans’ favor, though:

  1. The economy. If Republicans manage to tie a strong economy to the tax cuts they passed in December, it may convince enough middle-income voters to stick with them.
  2. Democrats shooting themselves in the foot. If they drift too far to the left, and wholly embrace a style of identity politics that confuses or repels a majority of Americans, it could give swing voters pause.

Watch these five blue states

Another one from Harry Enten:

California, Illinois, New Jersey, New York and Virginia account for only a small percentage of Republican-held seats overall, they are home to a disproportionate share of vulnerable Republicans.

25 Republican House seats in these five states could flip to the Democrats. That’s one more seat than they need for a majority.