Pennsylvania's new congressional district lines are not a game-changer

The Pennsylvania Supreme Court ...

Posted: Feb 20, 2018 2:01 PM
Updated: Feb 20, 2018 2:01 PM

The Pennsylvania Supreme Court has redrawn the state's congressional lines after declaring the current map an unconstitutional gerrymander.

The new lines are good news for Democrats. Under the old map, for example, Hillary Clinton won six of the state's 18 congressional districts. Under the new map, she would have won eight of the state's 18 congressional districts.

Still, the importance of the new map should not be oversold.

While the new map gives Democrats a better chance of taking back the House in 2018, it doesn't change the odds greatly.

You can do different types of fancy calculations, but Democrats are now probably favored in two seats that were at best toss-ups for them before: the new PA-5 and PA-6. Clinton would have won these districts by around 28 percentage points and 9 percentage points respectively under the new lines. Under the old lines, these were seats were carried by Clinton, but by just 2 percentage points or less.

A shift of two seats isn't small, though it's not exactly that large in the grand scheme. Democrats need a net gain of 24 seats to win the House in November. Two seats is less than 10% of that. You could certainly imagine instances where two seats made the difference in control of the House, though they are few and far between.

Now, the new map is beneficial to Democrats in ways beyond PA-5 and PA-6. The advantage that incumbents usually enjoy will be lessened by the new map because some Republican representatives will have many new and different constituents. Additionally, a few other seats shifted a few more points Democratic (e.g. the new PA-1), while the new PA-17 (represented currently by Keith Rothfus) shifted greatly toward the Democrats. It was won by Donald Trump by 3 points compared to 21 percentage points under the old lines.

Still, the political environment heading into 2018 will probably limit the effects of the new map. Because the national political environment is supposed to heavily favor the Democrats (for example, Democrats hold a 7-percentage-point edge in an average of recent live interview generic ballot polls), the incumbency advantage was already likely to be smaller. That's part of the reason why there were many Republican-held seats in Pennsylvania that Democrats already had a good chance of flipping under the old map.

Under the old map, the CNN House ratings had five Republican seats that were ranked lean Republican or worse for the Republicans. A sixth seat was considered likely Republican (i.e. a seat that could flip, but most likely not). Interestingly, that sixth seat, held by Rep. Lloyd Smucker, went from being won by Trump by 7 points to being won by Trump by 26 points. In other words, it's now much safer for the Republicans.

Let's take a closer look at the new map, taking into account the fact that Democrats hold about a 7-point lead on the generic congressional ballot. If you were to look only at the number of Republican seats that were won by Trump by 7 points or less or won by Clinton in 2016, the change from the old map to the new map is minimal. There were five Republican seats that met this criteria under the new map and four under the old map. Democrats will certainly welcome the one additional seat, but one seat is clearly not a game-changer.

Nationally, the number of Republican seats that are in danger of being flipped barely expanded under the new map. For instance, the number of seats won by Trump by 7 points or less or won by Clinton went from 45 to 46. The more limited playing field of Republican-held seats won by Clinton went up from 23 to 25.

It's also still the case that Democrats will have to win the national House vote by a fairly wide margin to take back the House.

Previously, I've calculated that to probably be between 5.5 and 8 percentage points. Based on some simplistic math that takes into account how many seats are now vulnerable for the Republicans and the fact that the party that has benefited from a wave has netted a pickup of approximately two-thirds of the number of vulnerable seats in the past few wave elections, Democrats may now only need to win the national popular vote by between 4.5 and 7 percentage points to take back the House. Again, that's better than it previously was for the Democrats, but it's a considerable margin and not all that different from what they needed before the Pennsylvania map was redrawn.

If Democrats want to greatly increase their chance of taking back the House, what they'll want is a change in the national political environment. Their generic ballot lead has fallen from a double-digit lead in December. If Democrats can get that lead back up to this margin, it would have a far greater impact on their hopes of taking back the House than the new map out of Pennsylvania will.

Mississippi Coronavirus Cases

Data is updated nightly.

Cases: 501097

Reported Deaths: 9990
CountyCasesDeaths
Harrison34338538
DeSoto32117403
Hinds31939628
Jackson24494382
Rankin21995390
Lee15543235
Madison14581280
Jones13851242
Forrest13453251
Lauderdale11991317
Lowndes11050188
Lamar10521135
Pearl River9533237
Lafayette8550140
Hancock7732127
Washington7438158
Oktibbeha7146131
Monroe6777177
Warren6694176
Pontotoc6664102
Neshoba6637206
Panola6531131
Marshall6467134
Bolivar6317148
Union602894
Pike5820152
Alcorn5669101
Lincoln5436135
George496879
Scott472898
Tippah469281
Prentiss467281
Leflore4658144
Itawamba4636105
Tate4588111
Adams4587119
Copiah448592
Simpson4446116
Yazoo444187
Wayne439772
Covington428894
Sunflower4239105
Marion4226108
Coahoma4160105
Leake408288
Newton381779
Grenada3707108
Stone360364
Tishomingo359792
Attala331589
Jasper329965
Winston314291
Clay308076
Chickasaw300367
Clarke292494
Calhoun279446
Holmes267987
Smith264050
Yalobusha234047
Tallahatchie228051
Greene219348
Walthall218763
Lawrence212940
Perry205556
Amite205156
Webster202946
Noxubee186740
Montgomery179656
Jefferson Davis171743
Carroll169138
Tunica159839
Benton148838
Kemper141941
Choctaw133426
Claiborne132737
Humphreys129538
Franklin120228
Quitman106428
Wilkinson105139
Jefferson94534
Sharkey64120
Issaquena1937
Unassigned00

Alabama Coronavirus Cases

Cases: 820011

Reported Deaths: 15407
CountyCasesDeaths
Jefferson1148361924
Mobile726091339
Madison52337697
Shelby37622350
Baldwin37258552
Tuscaloosa35117612
Montgomery34116740
Lee23536246
Calhoun22232488
Morgan20952378
Etowah19834500
Marshall18372304
Houston17390412
St. Clair16064339
Cullman15454293
Limestone15349199
Elmore15264286
Lauderdale14314295
Talladega13842283
DeKalb12662261
Walker11206370
Blount10197176
Autauga10047148
Jackson9874184
Coffee9211191
Dale8900185
Colbert8871201
Tallapoosa7089198
Escambia6775134
Covington6713183
Chilton6645162
Russell637059
Franklin5962105
Chambers5610142
Marion5007127
Dallas4975200
Pike4796106
Clarke475784
Geneva4574127
Winston4519103
Lawrence4324117
Bibb425286
Barbour357876
Marengo338390
Monroe331564
Randolph329764
Butler326496
Pickens316384
Henry312766
Hale311688
Cherokee302860
Fayette294180
Washington251651
Cleburne247760
Crenshaw245275
Clay243368
Macon234863
Lamar224447
Conecuh186253
Coosa180240
Lowndes175364
Wilcox168939
Bullock151744
Perry138840
Sumter133238
Greene126744
Choctaw88527
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