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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: 312926

Reported Deaths: 7226
CountyCasesDeaths
DeSoto21474257
Hinds20271414
Harrison17796309
Rankin13561278
Jackson13404246
Madison10062217
Lee9961173
Jones8364163
Forrest7644152
Lauderdale7178240
Lowndes6366144
Lamar621286
Lafayette6168118
Washington5322133
Bolivar4796132
Oktibbeha461198
Panola4556105
Pearl River4494145
Marshall4396103
Warren4376121
Pontotoc419372
Monroe4094133
Union408876
Neshoba4024176
Lincoln3947110
Hancock377086
Leflore3487125
Sunflower335790
Tate332384
Pike3294105
Scott315273
Alcorn311568
Yazoo310669
Itawamba299377
Copiah296065
Simpson294488
Coahoma294279
Tippah287668
Prentiss279360
Marion268780
Adams266082
Leake265573
Wayne262341
Grenada260186
Covington256381
George246748
Newton245961
Winston226881
Tishomingo225567
Jasper220848
Attala214173
Chickasaw207157
Holmes188673
Clay184754
Stone181833
Tallahatchie178140
Clarke177879
Calhoun169832
Yalobusha163336
Smith162234
Walthall133845
Greene130333
Lawrence128323
Montgomery126742
Noxubee126734
Perry125838
Amite122842
Carroll121728
Webster114532
Jefferson Davis106932
Tunica104726
Claiborne102230
Benton99025
Humphreys96133
Kemper95328
Franklin83423
Quitman80016
Choctaw76018
Wilkinson66930
Jefferson65428
Sharkey50217
Issaquena1686
Unassigned00

Alabama Coronavirus Cases

Cases: 530011

Reported Deaths: 10946
CountyCasesDeaths
Jefferson763591519
Mobile40875804
Madison34676503
Tuscaloosa25717451
Montgomery24308585
Shelby23389248
Baldwin21093307
Lee15844169
Calhoun14481313
Morgan14281279
Etowah13813353
Marshall12203222
Houston10553280
Elmore10036205
Limestone9952150
Cullman9647193
St. Clair9634239
Lauderdale9413241
DeKalb8821185
Talladega8210175
Walker7222277
Autauga6914108
Jackson6803111
Blount6645136
Colbert6291134
Coffee5503118
Dale4826111
Russell440038
Chilton4263111
Franklin425482
Covington4120117
Tallapoosa4006152
Escambia393276
Chambers3559123
Dallas3544151
Clarke350861
Marion3111100
Pike310177
Lawrence299898
Winston273772
Bibb260463
Marengo249164
Geneva248777
Pickens233760
Barbour230757
Hale222577
Butler215869
Fayette212062
Henry188744
Cherokee184345
Randolph179941
Monroe177040
Washington167039
Macon158650
Clay155956
Crenshaw151957
Cleburne148741
Lamar141834
Lowndes138553
Wilcox127029
Bullock123041
Conecuh110129
Perry107526
Coosa107128
Sumter104332
Greene92334
Choctaw60424
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