Princeton Election Consortium

A first draft of electoral history. Since 2004

Jul 13: Biden 380 EV (D+6.4% from toss-up), Senate 53 D, 47 R (D+5.6%), House control D+8.0%
Moneyball states: President AK AR IA, Senate MT KS ME, Legislatures KS TX NC

Election tracking 2020: U.S. House of Representatives

Despite the complexity of having 435 House races, a single survey quantity does a good job of tracking the House: the generic Congressional ballot (“do you support the Democrat or Republican for your local Congressional race?”). There are two reasons supporting this. First, districts are of equal population, and a national survey only has to weight them all equally. The first-past-the-post (plurality vote-getter wins) rule makes this simple. Second, regional differences average out in terms of how votes translate into number of seats won.

The black trace is a polling median. Its “averaging” rule is to take an N-week median of polls, one poll per pollster, the date defined by the last day that the poll was being conducted. For our House tracker, N=3.

The next task is to convert this voting tendency to representation. This is strongly dependent on how districts are drawn. In the U.S., districts are redrawn every 10 years. Because they have to be contiguous, they are constrained by how voters arrange themselves.┬áVoters favor Democrats by 30 points in urban areas, and Republicans by 15 points in rural areas. That 30%-vs-15% asymmetry creates a natural tendency for Democrats to be packed into fewer districts. It also provides the raw material for drawing lines to place them at a further disadvantage. In other words, natural geography is the starting point for partisan gerrymandering that we’ve seen explode since 2000.

We had to estimate what it would take for partisan control to switch between the parties. In 2018, I estimated the Democrats needed to win the popular vote by 6% (“D+6%”). This year, because of state court decisions in Pennsylvania and North Carolina, and because Democrats have more incumbents, I estimate that the threshold is lowered to D+3%. I base this on comparison with the historical pattern since 1948, plus analysis of current single-party gerrymanders. Think of it as analogous to a golf handicap, where the abstract ideal of majoritarian rule collides with the tradition of drawing districts.

This handicap is included in the graph above. The right axis shows the actual polling median, and the left-hand axis is the same median shifted by 3 percentage points, to show the actual advantage in terms of representation.

There is a second featyre. The orange line indicates the outcome of special elections since 2018. For the last few cycles, special elections have been a good predictor of how the national vote will go. This measure and the generic Congressional ballot are in approximate agreement. The same was true in the 2018 election. Of course, conditions can change. The black trace will always show a snapshot of current conditions. We will see whether the two measures continue to agree.

An open question in our democracy is whether the “handicap” above can be made close to zero, achieving similar treatment of the major parties, while still observing traditional districting principles. Achieving that outcome requires bipartisan or non-partisan control over redistricting. Another question is whether candidates of either party have to work for re-election, or are protected by a well-designed map. This is done best by independent commissions. To learn more about how to achieve those goals, see our work at gerrymander.princeton.edu.