Over the past few posts I have narrowed down the list of states where we might claim gerrymandering affected the outcome of the 2012 Congressional election. There is still one more task remaining — identifying those states where the partisan composition of the legislature and governorship, and the laws governing redistricting, enabled one party or the other to draw lines in a favorable manner. This table combines information on each state’s constellation of partisanship and the method by which the state allocates Congressional seats.
There are four types of apportionment methods identified by Ballotpedia. Most states place control over redistricting in the hands of the state legislature with the governor having a veto in all such states except North Carolina. Nine states use nonpartisan commissions, and another five states can appoint a commission if the legislature fails to agree on a plan. I treat those states as equivalent to states where the legislature is entirely in control. Iowa reverses the backup system, with the legislature brought in only if the commission fails to come up with a plan. I consider Iowa a commission state.
In the table above, I have divided the states into four groups. At the top we have the eight states with unified Democratic control of state government and laws that grant the legislature and governor control over the apportionment process. Some of the states identified in the last post as showing a pro-Democratic bias in their seat allocations like Massachusetts and Connecticut appear on this list of states with conditions favorable to Democratic gerrymandering.
Then follows a much larger group of states, nineteen, which had unified Republican state houses with control over redistricting. Again we see some familiar faces from earlier tables like Pennsylvania and Ohio. The third block of fourteen states have more uncertain gerrymandering conditions because of split partisan control either within the legislature or between the legislature and the governor. The last group of nine states rely on nonpartisan commissions to draw their lines. Both California and Arizona appear on this list despite showing a Republican and a Democratic excess of seats respectively.
So the last step is to combine the earlier list of states where gerrymandering might have taken place with the lists of states in the top two groups of the table above where the arrangement of political forces in the state might have encouraged gerrymandering.
Four of the eight states with pro-Democratic seat outcomes seem likely candidates for gerrymanderers. All told, the Democrats probably won between four and six additional seats in Massachusetts, Connecticut, Illinois, and Maryland than they would have under a fair allocation of seats. Gerrymandering seems much less likely to explain the additional Democratic victories in Georgia and Maine, where the Republicans were in control of the apportionment process, or in Arizona where district lines are drawn by a commission.
In Georgia, the entire process was controlled by the Republicans and was expected to produce a result favorable to that party. However one of the targeted Democratic incumbents, John Barrow, moved after his district was redrawn, contested the 12th CD, and won with 54% of the vote. Barrow’s dogged pursuit of his seat probably accounts for the “extra” Democrat in the Georgia delegation.
In New Hampshire, a Republican legislature faced off against a Democratic governor, though most of political struggles took place within Republican ranks. Both seats had been captured from the Democrats in 2010, and the two new incumbents squabbled over the small changes that needed to be made to balance the two districts population. In the event both seats were retaken by the Democrats in 2012. This Democratic surge in New Hampshire probably has much to do with the regional trends to the Democrats across New England, and the efforts by the Obama campaign to mobilize Democratic voters in a swing state.
Two states that showed a pro-Republican bias had lines drawn by a commission rather than the legislature, while in Virginia legislative control was split between a Democratic Senate and a Republican House. That leaves ten states with unified Republican control that show evidence of gerrymandering. At the top of the list we have Pennsylvania, Ohio, Michigan and North Carolina, all states that have been repeatedly cited by observers as being heavily gerrymandered in the Republicans’ favor. Unfortunately these observers often tend to claim the Republicans maintained control of the House entirely by gerrymandering and neglect the effects of incumbency.
At one extreme gerrymandering might have given the Republicans seventeen more seats in the House. That figure combines the minimal estimate for Democratic gerrymanders, four, with the maximal estimate for the Republicans of twenty-one. If those seventeen seats had been won by Democrats, they would have eked out a one-seat majority in the House. To achieve that value, though, we have to assume that urbanism only exerted effects in the Democratic states and had no effects in the Republican ones. The opposite set of assumptions leads to an estimate of gerrymandering effects of just eight seats for the Republicans, far too few to have changed the outcome in the House.
These results provide a lower- and upper-bound on the effects of gerrymandering. The actual effects probably lie somewhere in between. Perhaps about a dozen seats remained with the Republicans because of gerrymanders, hardly an insignificant number to be sure, but not sufficient to explain why the Democrats could not win control of the House despite winning a slight majority of the popular vote for Congress.