It is an article of faith among Democrats and some political commentators that a major barrier to Democrats retaking control of the House of Representative in 2018, or even in 2020, is Republican gerrymandering following the 2010 U.S. Census. Republicans, the narrative goes, used the governor’s mansions and state legislatures they controlled after the 2010 midterm elections to draw state legislative and U.S. House districts to their partisan advantage.
Gerrymandering is nearly as old as the Republic. The word “gerrymander” comes from Elbridge Gerry, the Massachusetts governor who supervised the redrawing of his state’s legislative districts (U.S. House, state senate, state house) to advantage his Democratic-Republicans following the 1810 U.S. Census. One new state senate district resembled a salamander, leading to the term “Gerry-mander” to describe the drawing of legislative district lines for partisan advantage.
However, outside of “compactness” and rough equality of population across districts of the same type in the same state (under the 14th Amendment’s Equal Protection Clause, per Reynolds v. Sims ), there is no official guidance for drawing legislative districts. Article 1, Section 2 of the U.S. Constitution says only that Representatives “shall be apportioned among the several States…according to their respective Numbers…[and] each State shall have at Least one Representative,” thus requiring the United States Census Bureau to determine every 10 years how many U.S. House members each state has (and thus how many electoral votes it has [# U.S. House members plus 2]). And the Voting Rights Act mandates majority-minority districts under certain circumstances.
What does not exist is a measure of how “fair” legislative districts are. That is why, until very recently, courts have been reluctant to overturn legislative district maps that may proffer a partisan advantage, yet still adhere to the requirements of compactness, relative population equality and, where necessary, the creation of majority-minority districts.
Naturally, I will now describe and analyze two potential, related measures of redistricting “fairness,” utilizing two-party vote for the U.S. House of Representatives.
Turning votes into seats. The first measure is the seat-to-vote ratio (SVR): the percentage of legislative districts (seats) won by a party in an election divided by the percentage of the vote won by that party. This is a straightforward concept—if one party wins 53% of the vote, you would expect that party to win (very close to) 53% of available seats. An SVR of 1.00 is a perfect correspondence of seats and votes, while an SVR greater than 1.00 suggests a partisan advantage.
Figure 1: Percentage Democratic U.S. House Seats and Two-Party U.S. House Vote, 1968-2016
Dem % Seats and Votes, U.S. House, 1968-2016
In 2016, Democrats won 47.6% of the total U.S. House vote, and Republicans won 48.7%, equivalent to 49.4% and 50.6% of the two-party vote, respectively (Figure 1). However, Democrats “only” won 44.6% (194) of the seats, when they “should” have won 49.4% (~215 seats; SVR=0.90). In other words, Democrats won 10% fewer seats than you would expect if seats and votes lined up evenly.
Just bear with me while I dive into the arcana of counting U.S. House votes. Feel free to skip the next six italicized paragraphs.
My sources for U.S. House election data are the biennial Statistics of the Presidential and Congressional Election reports published by the Office of the Clerk, U.S. House of Representatives (House Clerk). These reports tabulate votes for the Democratic and Republican candidates as well as for every other smaller party candidate (e.g., Libertarian, Green) as well as No Party Affiliation/No Political Party/Nonaffiliated/Nonpartisan, None of these Candidates (Nevada), Nominated by Petition (Iowa), Write-in/Other Write-in votes, Blank Votes (Hawaii, Maine, Massachusetts, New York, Vermont), Under Votes (Wyoming), Spoiled Votes (Vermont), Void (New York), Over Votes (Hawaii, Wyoming), Scatter/Scattering (New Hampshire, Wisconsin), All Others (Massachusetts) and Miscellaneous (Oregon).
California and Washington have all candidates for an office, regardless of party affiliation, run in a single “jungle primary” prior to Election Day. If no candidate receives more than 50% of the vote, the top two finishers face off on Election Day. In seven Congressional Districts (CD) in California and one CD in Washington, two Democrats faced off on Election Day, while one CD in Washington had two Republicans facing off on Election Day. I recorded all Democratic and Republican votes from these nine CD in my major party vote totals. Similarly, Louisiana holds their jungle primary on Election Day (with run-offs for the top two vote winners in December). I counted all Democratic and Republican votes on Election Day in my major party vote totals. Finally, Alabama, Georgia, Kentucky, North Carolina and South Dakota only list the Democratic and Republican candidates on their Election Day ballots.
Three states tabulate candidate votes from multiple party lines because smaller parties officially endorsed either the Democrat or Republican candidate for an office; the official House Clerk Democratic and Republican vote tallies exclude these minor party votes. Democrats in Connecticut received votes on the Working Families line, and Republicans received votes on the Independent line. In New York, Democrats received votes on the Working Families, Women’s Equality and, in CDs 2, 18 and 20, Independence lines, and Republicans received votes on the Conservative, Reform, Blue Lives Matter, Stop Iran Deal and, in CDs 1, 10, 11, 13, 19, 21, 23-25 and 27, the Independence line. In South Carolina, Democrats running in CDs 1, 2 and 7 received votes on the Working Families and Green lines. I included these smaller party votes in my major party vote totals because I also wanted to count the margin of votes separating the top two finishers in each U.S. House race.
In Minnesota, the Democratic Party is listed in CDs, 1, 4, 5, 7 and 8, while the Democratic-Farmer-Labor Party is listed in CDs 2, 3 and 6. Following Minnesota tradition, I counted all of these votes as “Democratic” in my major party votes totals.
Two states—Florida and Oklahoma—do not print unopposed candidates’ names on their ballots. This means that I have no votes for Democrat Frederica S. Wilson in Florida CD 24 and Republican Jim Bridenstine in Oklahoma CD 1.
For these reasons, while the House Clerk and I agree on a total of 129,888,395 votes cast in U.S. House elections in 2016, the House Clerk breakdown is 47.3% Democratic, 48.3% Republican, 4.3% All Other votes, while my breakdown is 47.6%, 48.7% and 3.7%–a difference that does not materially affect these analyses.
Figure 2: Ratio of Percentage Democratic U.S. House Seats and Percentage Democratic of Two-Party U.S. House Vote, 1968-2016
Dem Seat-Vote Ratios, U.S. House, 1968-2016
The Democrats’ 0.90 SVR in 2016 is in line with their 0.91 and 0.92 SVRs from 2012 and 2014 (Figure 2), suggesting that their disadvantage in converting votes to seats has been consistent since the 2010 redistricting.
However, as Figures 1 and 2 show, it is perhaps hypocritical for Democrats to yell too much about having SVR<1.00. Between 1968 and 1992, Democrats averaged 60.1% of U.S. House seats. They also averaged SVRs of 1.13 in the five elections following the 1970 redistricting (1972-80) and 1.11 in the five elections following the 1980 redistricting (1982-90), higher than the average 1.09 SVR for Republicans since 2010.
In 1994, the Republicans netted 54 U.S. House seats to win the majority for the first time since 1952, and they have held that majority for all but four years (2007-10) since. Still, in the five elections after each of the 1990 and 2000 redistricting processes (1992-2010), the U.S. House was, on average, evenly divided (50.1% Democratic) with an average SVR of 1.00.
In other words, when one party is consistently in the majority (Democrats in the 1970s and 1980s; Republicans since 2010), their SVR tends to be greater than 1.00. But is that a sign of systematic bias (partisan redistricting) or merely success at winning a majority of close elections?
One way to address this question is to examine results at the state level.
Seven states (Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont, Wyoming) have only one U.S. House member, rendering gerrymandering moot. Four states (Arizona, California, Idaho and Virginia) use an independent commission for redistricting, ostensibly removing political motivations from redistricting.
Removing the 82 U.S. House seats in these 11 states leaves Democrats with 145 (33.8%) seats after the 2016 elections, and 47.7% of the two-party vote, for a SVR of 0.71. That is, in the 39 states where partisan gerrymandering could happen, Democrats won 29% fewer seats than would be expected based upon their two-party vote share. In these states, moreover, Republicans netted 21.7 “extra” seats (Table 1).
Table 1: 2016 U.S. House Election Results in 39 States Where State Legislatures Control Redistricting
|State||U.S. House Seats||Democratic % 2-Party Vote||Actual Democratic Seats||Expected Democratic Seats||Actual – Expected|
In 17 of these 39 states, Republicans won at least one full seat more than expected from their two-party vote share, totaling 30.5 “extra” seats, while in seven states, Democrats won at least one full seat more than expected from their two-party vote share, totaling 9.6 “extra” seats.
So is this clear evidence that gerrymandering cost Democrats 21 or 22 U.S. House seats in 2016 (nearly the 24 they need to win back control)? Or, as suggested earlier, is it simply that parties with SVR>1.00 simply do a better job of winning close elections?
The marginals have vanished. Let’s define a “close” election as one decided by less than 10 percentage points and/or where the winning candidate received less than 55% of the total vote. In the four states where Republicans won at least two full seats more than expected from their two-party vote share (Pennsylvania, Texas, North Carolina, Ohio; total=12.3 seats), there were only four close elections (out of 83); Republicans won three of them for a net of two seats. There were zero close seats in the three states (Massachusetts, Connecticut, Maryland; total=5.3 seats) where Democrats won at least 1.5 more seats than expected from their two-party vote share.
In fact, only 47 U.S. House races (10.8%) met this definition of “close” in 2016. Republicans won 27 of them, for a net of seven seats–only one-third of the total advantage Republicans had in winning U.S. House seats in 2016 using the SVR measure.
In 2016, Democrats won their seats by an average 43.4 percentage points, while Republicans won their seats by an average 34.4 percentage points: the vast majority of U.S. House seats are extremely safe. Even if you exclude the 59 CD (13.6%) where candidates of one major party ran essentially unopposed (31 Democrats, 28 Republicans), the average winning margin was still 35.1 percentage points for Democrats and 26.9 percentage points for Republicans.
And that leads us to a second measure of redistricting “fairness”: extraneous votes (ExV).
To win a U.S. House election, you simply need to receive one vote more than your nearest opponent; all other votes are extraneous. For example, Democrat Carol Shea-Porter defeated Republican Frank Guinta in New Hampshire CD 1 by 162,080 to 157,176 votes. Ms. Shea-Porter only NEEDED 157,177 votes to win, meaning that she received 4,903 “extraneous” votes. By contrast, Democrat Dwight Evans defeated Republican James A. Jones in Pennsylvania CD 2 by 322,514 to 35,131, fully 288,382 votes more than he needed.
This matters because, ever since Governor Gerry and his salamander-shaped state senate district, partisan gerrymandering has meant packing as many of one party’s voters (Party A) into as few (very safe because filled with extraneous voters) legislative districts as possible. The other party’s voters (Party B, in control of redistricting) would then be spread across the remaining (somewhat less safe, with fewer extraneous voters) legislative districts. Evidence for partisan gerrymandering would thus be if one party tends to have more extraneous votes.
And there is such evidence. In 2016, Democrats averaged 112,222 ExV and Republicans averaged 98,582, meaning Democrats averaged 13.8% more ExV than Republicans. Narrowing the analysis only to the 39 states where partisan redistricting is even possible closes the gap: 111,401 to 102,963, with Democrats averaging 8.2% more ExV. Further removing seats with candidate(s) of only one major party reduces the absolute gap to 97,701 to 89,970, with Democrats averaging 8.9% more ExV than Republicans.
Table 2: Extraneous Votes for Winning U.S. House Candidates, and State Seat-Vote Ratios for Eight States, 2016
|State||Average Democratic ExV 2016||Democratic U.S. House Seats 2016||Average Republican ExV 2016||Republican U.S. House Seats 2016||2016 SVR|
There were eight states in 2016 where Republican U.S. House candidates won at least 1.5 more seats than expected from their two-party vote share (Table 1), for a total of 19.3 seats. Across these eight states, Democrats were also well behind on both measures of redistricting unfairness, averaging 24,625 more ExV and a SVR of 0.60 (without Texas: 45,023 ExV and SVR=0.57). Following the 2010 elections (and thus the 2010 U.S. Census), all but North Carolina had a Republican governor and all had state legislatures controlled by Republicans.
There is thus reasonably compelling evidence that Democrats were on the losing end of partisan redistricting in these eight states that was not nearly countered by controlling the post-2010 redistricting process in such states as Massachusetts, Connecticut and Maryland.
What this means for Democrats—and for democracy. There is nothing Democrats can do until after the 2020 U.S. Census to reverse the post-2010 redistricting. The first step, of course, would be to control governor’s mansions in these eight states in Table 2 following the 2020 midterm elections. This would require Democrats to hold governor’s mansions in North Carolina and Pennsylvania; win open races in Georgia, Michigan and Ohio; and defeat incumbent Republican governors in Indiana, South Carolina and Texas. They also need to chip away at Republican control of these state legislatures. If I were in charge of the Democratic Party, this is where I would focus my energy.
But there are two larger problems that I see, neither of which is good for our democracy because of the ways they impact partisan polarization and the responsiveness of elected officials.
The first problem stems from a limiting factor on drawing legislative district lines: where each party’s voters live. If Democratic and Republican voters are scattered evenly across states, partisan redistricting is much harder.
The fact, however, is that voters are NOT evenly distributed across states. Democrats primarily self-segregate into large urban areas and college towns, the Atlantic and Pacific Coasts, and majority-minority counties (e.g. the southern “Black Belt,” northern New Mexico, southwestern Texas). And while this self-sorting may allow Democrats to win state races by winning large majorities in a few overwhelmingly Democratic counties, it also makes it easier for Republicans to create a few safe Democratic CDs and state legislative districts in a state while carving up the rest of the state for themselves.
To be fair, many of these CDs are majority-minority as dictated by the Voting Rights Act, but there is a difference between winning 90% of the vote and winning 55% of the vote. To a large extent, Democrats have been complicit in adverse redistricting by allowing for the creation of super-majority-minority CDs.
For example, consider the 2016 election results in Pennsylvania (Figures 3 and 4, taken from here and here):
Figure 3: Pennsylvania Counties won by Democrat Hillary Clinton (Red) and by Republican Donald Trump (Blue) in 2016
Figure 4: Pennsylvania Congressional Districts won by Democrat (Blue) and Republican (Red) in 2016
Just six of Pennsylvania’s 67 counties (9.0%) accounted for 57.9% of Hillary Clinton’s vote in that state: five southeastern counties around Philadelphia and Allegheny County (Pittsburgh). In total, she won 11 Pennsylvania counties (16.4%), accounting for 67.1% of her statewide total.
Democrats won only five of 18 Pennsylvania CDs in 2016. Three of them (1,2,13) are clustered in the southeastern corner of the state (average winning margin 81.6 percentage points); the Democrats also won a Pittsburgh-area CD (14) by 48.7 percentage points and a Scranton-area CD (17) by 7.6 percentage points.
Do you see the problem?
Democrats won CDs 1, 2 and 13 in 2016 by an average 239, 757 votes; they are bordered to the north, south and west by CDs 6-8, which Republicans won by an average 52,676 votes. If Democrats control the post-2020 redistricting in Pennsylvania, they theoretically could redraw CD boundaries to shift enough Democratic voters from CDs 1, 12 and 13 into CDs 6-8 to make the latter CDs no worse than swing districts, while keeping the former CDs in Democratic hands, partially winning back the 3.3 “extra” seats Republicans won in 2016 (Table 1).
But nothing would be guaranteed and Democrats could end up violating the rules of compactness and relative population equality. Also, the population of Pennsylvania CD 2 is 61.2% Black; redrawing it could run afoul of the Voting Rights Act.
The other two Democratic seats in Pennsylvania offer little aid. Michael Doyle won his CD 14 by 167,294 votes, while Republicans won the bordering CDs (12, 18) by 84,498 and 293,684 votes, respectively; Tim Murphy was unopposed in the latter race. And Matt Cartwright only won his CD 17 by 22,304 votes; not very many Democratic votes to spare there.
So, Democrats’ best chance to make Pennsylvania’s redistricting more “fair” lies in just three CDs in the southeastern corner of the state because that is where the vast majority of the state’s Democrats are. It would almost be easier for Democrats either to win (back?) voters in the rest of the state or to redistribute themselves across the state, neither of which is necessarily all that easy.
And this is broadly true for Democrats nationwide, who would need to flip a net 24 CDs to win back control of the U.S. House in 2018 (since 1970 the average seat loss for the party holding the White House in its first midterm election [n=7] is 24.1). The path of least resistance is to win back the 27 “close” seats won by Republicans in 2016, while losing no more than three of the 20 “close” seats they won; Republicans won 12 of those 27 seats by more than 10 percentage points.
Talk about threading the needle!
This leads us to the second large problem. Even though Democrats are behind on both the ExV and SVR measures, Republicans also had very high average winning margins and extraneous vote totals. BOTH parties are drawing safer and safer CDs for themselves, a trend Yale political scientist David Mayhew first pointed out in 1974.
This lack of competition makes U.S. House members (and legislators generally) more worried about being challenged in a primary (from the left for Democrats and from the right for Republicans) than they are of losing the “swing” voters. When elected officials are more responsive to the median voter in their own party than they are to the median voter in their district (or state), their incentive to cooperate and compromise with elected officials of the other party diminishes accordingly. This leads to legislative gridlock, meaningless “gotcha” votes and increased political polarization.
If partisan gerrymandering exists, and if it then leads to such perverse incentives, then it should viewed not as threat for one political party, but for our democracy more generally.
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 I use two-party vote (i.e., the percentage Democratic and percentage Republican of the votes cast only for those two parties) because I will, inter alia, compare percentage of votes won to U.S. House seats held. Every House member is either a Democrat or a Republican, so including third-party votes in calculating these percentages would be misleading.
 Hawaii and New Jersey use a “political commission” for redistricting. As I am uncertain how free from partisan pressures these commissions are, I choose to include them from these analyses.
 Or faced primarily third-party opposition, including the three Arkansas Republicans whose closest opponent was a Libertarian.
 In 34 CDs, only one major party fielded candidates while smaller parties (usually Libertarians) fielded candidates. the extraneous votes is relative to “all other votes combined.” This increased the average ExV for Democrats and Republicans, only marginally affecting the analysis, as shown later in the paragraph.
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