Friday, May 31, 2013

9-4 Michigan Congressional Map in 2020

Some folks have already begun discussing what will happen to Michigan in the 2020 redistricting cycle, so I'll weigh in as well.  If Michigan keeps 14 districts, an incumbent protection map is likely, with small shifts necessary to account for changes in population.  However, Michigan has lost at least one congressional district for each of the last several cycles, and will probably lose another next time.  Republicans currently have a 9-5 advantage in the congressional delegation.  Can they stretch it to 9-4?  Yes, as the following map shows.
I should note that I am assuming that the population trends that have affected Michigan over the previous decade will continue.  In the previous decade, Detroit lost 240,000 people.  I assumed that Wayne County will lose another 100,000 people.  According the census estimates, it has lost 28,000 in the last two years.  Hence I overpopulated the Detroit districts by 50,000 each, and underpopulated the Republican districts 10000-15000 each to compensate.  It is just barely possible to maintain two black majority districts with these numbers, which leaves little flexibility for how to draw them.
Many people have identified Sander Levin's 9th district as the most likely to be dismantled, and I agree.  I drew the two Detroit districts to pick up the most democrat parts of his district, with the rest going to two Republican districts.  The metro Detroit Republican districts have to change significantly to account for this.  John Dingell's Downriver/Ann Arbor district is mostly unchanged.
The key to the map, though, is the 5th district.  It currently contains Flint, Saginaw, and Bay County, along with some Republican and swing territory nearby.  There aren't any major dem areas adjacent to the district.  Packing it as efficiently as possible requires adding Lansing and East Lansing, with Shiawassee as a connector.  This moves the district 5% to the left, and allows Republican districts in metro Detroit to take a few democrat areas, including Royal Oak and Westland.
Michigan redistricting has followed the Apol standards for the past few decades.  Loosely speaking, they require minimizing county breaks.  This map does not, though it is close.  It may be possible to eliminate one or two breaks by shuffling around some territory in the West Michigan districts, depending on how exactly the populations end up.  It is important to remember that the Apol standards are a law that can be overridden by any other law, so they are really a strong tradition rather than an absolutely binding rule.
Here is the map.




Here are the district descriptions with McCain 2008 and 2006 GOP average data.
1: 48.4/54.9 (unchanged) The UP and Northern LP.  Adds a few counties for population.  This district is never safe, but it has been trending Republican in recent years.
2: 49.0/61.7 (moves about 1.5% left, which it can afford)  West Michigan.  Adds a chunk of Grand Rapids.
3: 50.2/62.4 (moves about 1.5% right) Kent, Calhoun.  Adds some of Eaton.
4: 48.5/57.9 (unchanged) Central Michigan. Not much changes.
5: 30.6/40.5 (3-5% left) Lansing, Flint, Saginaw, Bay.  Pretty clean, too.
6: 45.5/56.1 (moves a hair right)  SW Michigan.  Adds Branch and Hillsdale.
7: 48.6/58.9 (about 1.5% right)  Livingston, Monroe, Lenawee, parts of Jackson, Ingham, Washtenaw.  Walberg and Rogers' bases are both here.
8: 48.3/60.2 (about 1% right) NW Wayne, W Oakland, S Genesee.  State senators Pat Colbeck or Dave Robertson would like this district.
9: 31.7/42.6 (not much change) Downriver and Ann Arbor.  Bet on someone named Dingell representing this.
10: 49.3/58.9 (about 1% left) N Macomb, St. Clair, the Grosse Pointes.  Loses the Thumb, adds the Grosse Pointes, Sterling Heights, and St. Clair Shores.  Safe for any Republican incumbent; could be vulnerable to a Macomb democrat if open.
11: 49.0/61.2 (a bit right) E Oakland and the Thumb.  Parts of the existing Miller, Rogers, and Bentivolio districts.
12: 18.9/28.4 (51.6 Black/50.2 Black VAP) E Detroit, S Macomb
13: 19.0/29.5 (52.6 Black/50.9 Black VAP) W Detroit, Pontiac, Farmington, Southfield, Romulus

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