The 2011 House redistricting, state by state

Robert Draper in the latest Atlantic magazine says:

[R]edistricting today has become the most insidious practice in American politics—a way, as the opportunistic machinations following the 2010 census make evident, for our elected leaders to entrench themselves in 435 impregnable garrisons from which they can maintain political power while avoiding demographic realities.

Draper focuses special attention on redistricting in Texas and North Carolina as examples of partisan gerrymandering by Republicans, though he also mentions Illinois and Maryland as examples of gerrymandering on the Democratic side.  (He also cites California as a gerrymander engineered by Democrats through the new Citizens Redistricting Commission.  But this story, and the supposed Democratic seat gains it depends on, have been pretty thoroughly debunked.)

In a recent post in our series on the 2012 House elections, we concluded that the redistricting had no effect on the predicted partisan breakdown in the House this fall.  But even if the overall effect is zero, what is the effect in individual states?  Can we find evidence for the gerrymandering Draper mentions?

The graph below shows our predictions for individual states, organized by the size and direction of the Democratic seat gain or loss (h/t to Jonathan Kastellec and Eduardo Leoni for the R code that forms the basis of this graph):

We predict no change for 33 states.  We do find evidence for the gerrymanders Draper mentions in North Carolina (-2 Democrats) and Illinois (+2 Democrats).  But not much is happening in Maryland.  And the largest Democratic gains were in Florida (3 seats) and Texas (2 seats), where Republicans were in control, while the party’s largest losses aside from North Carolina are in Massachusetts and New York, where the Democrats were in control (2 each).  (h/t to Justin Levitt for his breakdown of party control.)*  Why would a party allow itself to lose seats?

One factor we haven’t yet considered is reapportionment, which changed the total number of seats in each state, making it harder to maintain the status quo.  To get a handle on this problem, we imagined how a bipartisan redistricting process would approach it.  First, it would probably try to divide as many seats as possible evenly between the parties.  A state with a two-seat gain would give one to each party, a state with a four-seat gain would give two to each party, and so on.  We can treat these changes as “expected” and subtract them out.  However, states with an odd number of seats lost or gained will always have one seat that can’t be split.  We’ll treat this last seat as a pure redistricting effect and not correct for it.  (The only exception is Massachusetts, where all the seats were held by Democrats so the state’s one-seat loss from reapportionment had to come from that side of the aisle.)  The end result of all these adjustments looks like this:

New York and Massachusetts now look better for Democrats, but still a loss of one seat for each.  Likewise, Texas and Florida look worse for Democrats, but they’re still holding their own or coming out ahead.  The adjustment also makes Ohio look like a Democratic gain, since the state lost two seats but the Democrats are in shape to lose none.

Looking at these results, party control of the redistricting process has been a bust.  Only three states with total one-party control produced plans with the expected partisan change:  North Carolina (-2 Democrats), Oklahoma (-1 Democrats), and Illinois (+2 Democrats).  At the same time, several states had one-party control that produced a gain for the other party:  Massachusetts, New York, Arkansas, Ohio, and Florida.  So we’re back to the original question:  what gives?

Several possibilities come to mind.  The simplest is just that our model is missing something.  It only takes into account the presidential vote in the district and whether an incumbent is running, plus some national level factors.  This captures a lot of what a gerrymandering party would have available to it, but not everything.  Personal characteristics of the incumbent, detailed knowledge of the demographics and politics of the district, as well as an understanding of strong potential opponents who also live in the area would all facilitate drawing a more effective gerrymander.  Not to mention the dynamics of the ultimate campaigns run in each district, which cannot be known at the time of the redistricting but might dictate a different outcome in specific cases.

But there are a couple substantive reasons to expect this result.  First, a redistricting party doesn’t have free reign to do as it pleases.  Districts must be equal in population (the allowed deviation between districts is vanishingly small), the Voting Rights Act constrains activity in many states, and some states also have specific rules that limit the options.  (Along these lines, Florida voters recently imposed boundaries on what the legislature could draw, and Texas’s lines ended up being drawn by the courts.)  Moreover, a party’s desire for more districts can often conflict with its own incumbents’ desire for safe reelection.  And a redistricting party must work with the state it has, not the one it wants.  Republicans and Democrats may not live in close enough quarters to permit the sort of seat-maximizing gerrymander a party would otherwise want.

Finally, these numbers may reflect the core reality of this election:  Republicans are at historic highs and don’t have much room to grow.  Ohio is a perfect example of this.  The state is a toss-up and even leans Democratic in the presidential race, yet Democrats currently hold only 5 of 18 seats.  The state lost two seats from reapportionment; what are the chances Republicans could bring the Democrats down to 3 out of 16?  You can’t squeeze water from a stone.

None of this means we should ignore the signs that some states, like North Carolina or Illinois, have gerrymandered, or that we might not have more signs of gerrymandering by looking carefully at specific states.  It’s just to say that gerrymandering, broadly considered, is not a big part of the picture.

*Because our model has error, the sum of all these predicted changes is a one-seat loss for Democrats rather than the aggregate one-seat gain we predicted before.  But this is certainly within the expected range.

15 Responses to The 2011 House redistricting, state by state

  1. Andrew Gelman September 28, 2012 at 8:25 am #


    This shouldn’t be a surprise in light of my 1994 APSR paper with Gary King. The biggest effect of redistricting is to reduce partisan bias.

    • Eric McGhee September 28, 2012 at 12:02 pm #

      Yes, Andrew–apologies. I didn’t link to political science research like I should have. Bruce Cain and Richard Born would also support some form of the “partisan effects are small” argument, I would think.

  2. FreeDem September 28, 2012 at 8:39 am #

    I’m confused. Is your model not predicting a gain of a Democratic seat in Maryland at all, or is it attributing that gain to something other than redistricting? If you’re not predicting a gain of a Democratic seat in Maryland at all I would fundamentally question your model.

    • Eric McGhee September 28, 2012 at 11:47 am #

      We predict no gain in Maryland. That’s based on the national climate, the presidential vote in each district, and whether an incumbent is running. Incumbency and presidential vote by themselves lock up one seat for Republicans (1) and six seats for Democrats (2, 3, 4, 5, 7, & 8). That leaves the 6th, which leans Democratic in the presidential vote but has an incumbent (Bartlett) running. Predicting that race as a Republican win is hardly crazy, though the dynamics of it appear to have shifted to the Democrats according to most handicappers. (Though as recently as July there was a Democratic poll that put Bartlett down by only two.)

  3. Andrew Rudalevige September 28, 2012 at 8:40 am #

    Draper seems to be specializing in the overly dramatic claim recently. See too his October piece in GQ — “Whatever happens in these three presidential debates will, in all likelihood, determine who takes the oath of office three months later. That’s not an overstatement.”

    Um, yes, it is.

    The full piece (which has some nice material, especially on the Romney gubernatorial run in 2002) is at .

  4. J September 28, 2012 at 10:42 am #

    As an Ohioan I have to object to the claim about the D+1. The two seats that were lost (realistically it was Kucinich and Kaptur thrown in together in Northern Ohio as well as Renacci and Sutton and then the squeezing of a Dem swing district in the Cincinnati area) sured up the map but I find it hard to believe that this is a net positive for Democrats.

    • Eric McGhee September 28, 2012 at 11:54 am #

      It’s only a net positive if you believe our reapportionment “adjustment.” But think of it this way: Republicans currently hold 13 seats. Even if you believe only the handicappers, the best case scenario for Republicans is a loss of one seat for each party. In terms of control of the House, that’s a wash.

  5. Dave Ely September 28, 2012 at 1:31 pm #

    There is another factor that you should consider in your model. Population shifts within the state can force changes, or limit what is possible. You should include a measure of over and under population for pre-existing districts as it relates to partisan character. If one party hold districts that are consistently over or underpopulated, a perfectly neutral redistricting would be expected to produce a partisan shift.

  6. Brendan September 28, 2012 at 2:10 pm #

    I think the analysis misses a few important things which means that both Draper and you can be right. You may be right that gerrymandering may not have a huge effect on 2012 but that doesn’t mean that it doesn’t have a large effect on overall election results.

    A couple of critiques to why I think that your analysis deal with Draper’s conclusions directly.

    1. You said last week that democrats will likely get 50% of the votes and 45% of the vote. Taken over 500 data points and from your comments a generally positive view of democratic performance compared to 2010 (based on your comments), I think that this still shows a significant impact of gerrymandering overall. From a practical perspective, there are diminishing returns on gerrymandering and my guess is that most of the impact has already been squeezed out of the minority parties in 1990 and 2000.

    2. Since you only looked at Democratic +/- in the re-apportionment adjustment, you aren’t capturing net gains for Republican’s. If I read your re-apportionment chart correctly, you see -9 and +6 so a net -3. For example, Texas added 4 seats and Utah 1. Under your re-apportioned chart, those are both +0 for D so that is +4 and +1 for R. I wonder if it would be better to use R minus D as a baseline and measure from that value for the re-apportionment analysis. I think this analysis would show you how majority parties dealt with changes in their apportionment and you could determine if those seats were being gerrymandered to increase the balance in those states.

    Another analysis that might show overall effects of gerrymandering would look at balance changes where party control has changed between 2002 and 2012.

  7. Modaca September 28, 2012 at 2:38 pm #

    I think it should be “free rein,” not free reign.

  8. Ben Bishin October 1, 2012 at 10:57 am #

    I may have missed something, but I think these data are not sufficient to conclude that party control of the redistricting process has been a bust. There is significant variability in the goals and effectiveness of the parties across states, (partly because the majority in different states has different goals) but any measure of this has to compare the party breakdown to the partisan breakdown of voters in the state itself. That is to the extent that party control of these processes did not change, the advantage may have already been built in. So, for instance, Florida is a very slightly Republican state, but before this redistricting round, their House delegate was 18R-7D (and the state houses had even larger margins for the GOP) because the GOP was incredibly effective. Conversely, California had an incumbency gerrymander so Democrats there did not max out the number of seats they could control.

    • Eric McGhee October 1, 2012 at 11:50 am #

      These are good points. I think we were just evaluating the naive “party control = more seats” idea. This is the idea that has the most direct political meaning (who cares how you get more seats as long as you get them?) but there’s a lot more to it than that. As you say, the reference point is critical for evaluating the concept of partisan redistricting in general, and we didn’t do that here.

  9. MS October 1, 2012 at 11:16 am #

    Your model omits that seats in most states are already gerrymandered. The question isn’t whether the latest round of gerrymandering an already-gerrymandered set of districts can tweak out any more seats for one party – you’ve answered that above, and the answer is “yes, but only a few”. But that’s a dumb question. The marginal amount of extra corruption in 2010 doesn’t matter to anyone. The question should be, “how many seats are being pushed to one side or the other compared to a set of fair districts”, for example ones allocated by a computer attempting to minimize the area allocated to each district without regard to the partisan character of the district? And the answer to that question is “a lot”.

    Your conclusions above would leave people with the belief that gerrymandering is only having a little effect on US elections, which is very very far from the truth.

    • Eric McGhee October 1, 2012 at 11:52 am #

      MS: see my response to Ben Bishin above. Our goal wasn’t to evaluate whether gerrymandering occurs, but to see whether party control in this cycle has altered the partisan status quo.

  10. Jeremy October 5, 2012 at 1:18 pm #

    I’m surprised no one’s mentioned that New York was a nonpartisan redistricting. The Republican State Senate and Democratic Assembly could not agree on a map. In the past, the two parties worked out a plan to protect incumbents, but this time it went to the courts, where the new map was drawn. I suspect the Democrats losing a seat was due to the court relying heavily on the compact and contiguous standard which favors rural voters who are more likely to vote Republican.

    What do you think?