One National Capital, Two Cities

Who’s up for some DC primary statistical analysis blogging?
I thought so! (I admit, I’m a pale imitation of Nate Silver, but here goes.)
Yesterday was the Democratic primary for mayor of Washington, DC. Vincent Gray beat the incumbent mayor Adrian Fenty 54% to 45%.
The vote trend was incredibly split with the black-majority precincts going heavily for Gray while the affluent SWPL precincts went strongly for Fenty.
The split wasn’t just big; it was massive. I think the pronounced racial/geographic divide is the major under-reported story of this election.
There were precious few “swing” precincts. Consider this: Of the 143 precincts, the standard deviation of Fenty’s vote was over 25%.
Check out the distribution of Fenty’s vote:

Lower Bound Upper Bound # of Precincts
Over 85% 1
80% 85% 14
75% 80% 16
70% 75% 8
65% 70% 2
60% 65% 2
55% 60% 5
50% 55% 5
45% 50% 4
40% 45% 10
35% 40% 7
30% 35% 7
25% 30% 9
20% 25% 10
15% 20% 26
10% 15% 17

A majority of DC voters live in a precinct that went 75% or more for one candidate. In just 12 of the 143 precincts did both candidates come within 5% of their city-wide total. The results also suggest that votes were more polarized than polling indicated — perhaps an odd double Bradley Effect.
(Note: These numbers are based on the unofficial returns that were listed on the DC Board of Election’s website earlier today. Here’s a spreadsheet of the results.)

Posted by on September 15th, 2010 at 9:58 pm


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