Another week, another dramatic Republican primary, this time a runoff. Senator Thad Cochran eked out a narrow win against Chris McDaniel by appealing to Democrats in general and African-American voters in particular. How effective was this strategy? What changed between the primary and the primary runoff?
First, mapping the changes. If you want to see maps of the results, they're here. Below, on the left, we have turnout increase from the primary to the runoff. In the middle, how Cochran's share of the vote changed from the primary to the runoff. And on the right, the results of the 2012 presidential election. These are all repeated in the second set of maps in cartogram form, where the size of each county is proportional to the total number of votes in the runoff election.
It's clear that McDaniel took partial advantage of the favorable landscape the state presented to him. Turnout went way up in the northern part of the state, and so did his vote share.
Sadly for McDaniel, however, Cochran's strategy paid off big time. A massive increase in voters in Hinds County—the dark purple part of the blob in the middle of the cartogram—along with a decent increase in Cochran's vote share provide an increase in margin of 5,300 votes in that one county alone. In other counties where Obama had more than 60 percent of the vote, turnout also soared. Only a handful of counties—all of them red—had reduced turnout. Runoffs are typically lower turnout than the initial go-around, but not this time.
Below, some calculations that show at least 10,000 Obama voters took part in this runoff primary election.