Social Science Statistics Blog

• Indiana was off by about 3%: I had predicted 53.5% Clinton, 46.5% Obama; the result was 50.6% Clinton, 49.4% Obama.
• North Carolina was near spot-on: I had predicted 58% Obama, 42% Clinton; the result was 57.3% Obama, 42.7% Clinton.
• I significantly underestimated turnout: there were 1.27 million votes in IN and 1.53 million, while I had predicted 950,000 and 1.2 million, respectively.

I'm less worried about the turnout discrepancy; it happened because there had been no semi-open Democratic primary since Huckabee dropped out of the Republican contest. I was forced to use Pennsylvania (a closed primary) and Ohio (a semi-open primary, but with Huckabee still formally in) to predict turnout, which resulted in my underestimates. I'm more confident about my turnout projection in West Virginia, which is a semi-open primary, now that I have North Carolina to use as a predictor.

In predicting voter shares, my overall county-level correlations were .81 for Indiana and .88 for North Carolina -- on the whole pretty good, but with some problems. Below are spatial plots of residuals for North Carolina, and Indiana's appear above. Dark red corresponds to overestimation of Obama's support, and dark grey to underestimation of Obama's support.

Error	Actual	Predicted

The biggest mistake in my North Carolina predictions came with rural Blacks, who had not appeared significantly in my training data. The largest-magnitude residual was Greene County, a rural county that's 50% White and 40% Black (it's the small dark red). I projected a 70%-30% Obama victory, as is typical for counties with this racial split (note that among Democrats in such a county, Blacks will dominate). But somehow Clinton actually won this county 53% to 47%, putting me 23% off. In all of the neighboring rural black counties I had similarly overestimated Obama's support. This points to a possible interaction effect -- that rural blacks are more pro-Clinton than urban blacks.

Now to my top-line West Virginia prediction: Clinton 70.5%, Obama 29.5%, with a turnout of 300,000 votes. The map is below. I have Clinton taking every county in the state. Obama comes closest in Jefferson (a high-income, well-educated county next to Virginia) and Monongalia (a well-educated urban county that’s part of Pittsburgh tri-state).

With Clinton's impending departure, however, I plan to abandon these projections and move on to other fun. I really want to try a language model on Obama's and McCain's speeches.