Revisiting My Primary Forecasts

My original forecasts for Ron Paul’s primary performances are here. Those forecasts were based simply on the Iowa result, so it was quite possible that there would substantial error, and indeed there has been. Paul significantly overperformed his forecast in New Hampshire and South Carolina, the forecast was dead on in Florida, and then Paul underperformed significantly in Nevada. In yesterday’s elections, Paul did significantly worse than expected in Colorado, slightly worse than expected in Minnesota, and slightly better than expected in Missouri. In general, he seems to be doing worse than expected since Florida.

Why is that? It could be that my forecast model was an unbiased model at the time, but that circumstances have changed unfavorably for Paul’s candidacy. Certainly, recent good economic news probably doesn’t help an antiestablishment candidate like Paul. Perhaps his poor Florida performance, although it should have been anticipated, demoralized some of his supporters. On the other hand, my forecast model could have been wrong, particularly in assuming that Paul’s vote shares would continue to feature overdispersion. It’s possible that with a broadening voter base, Paul’s caucus advantage has declined. Thus, Paul should improve on his 2008 performances everywhere, but not in a manner proportionate to his 2008 performances: there will be some apparent regression to the mean.

To see how Paul’s 2012 performances are stacking up against his 2008 performances, I ran a regression on the states with results so far. First, I regressed 2012 performance against 2008 performance linearly. Here are the results:

lm(formula = vote12 ~ vote08)

    Min      1Q  Median      3Q     Max 
-5.0465 -3.8563  0.8463  2.0316  6.8799 

            Estimate Std. Error t value Pr(>|t|)  
(Intercept)   6.9290     3.4156   2.029   0.0888 .
vote08        1.1807     0.3632   3.251   0.0175 *
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Residual standard error: 4.444 on 6 degrees of freedom
Multiple R-squared: 0.6378,     Adjusted R-squared: 0.5775 
F-statistic: 10.57 on 1 and 6 DF,  p-value: 0.01745

These results suggest that for every 1% in 2008 vote share in a state, Paul is now receiving 1.2% in 2012, in addition to a base of 6.9% everywhere – so getting 5% in a 2008 primary would be associated with a forecast of about 12.9% in 2012. With these eight data points, the simple model explains 63.8% of the variance in 2012 performance.

Next, I turn to a log-linear model, which would be more appropriate if Paul’s performances continue to experience overdispersion. Here are the results:

lm(formula = lnvote12 ~ lnvote08)

     Min       1Q   Median       3Q      Max 
-0.36483 -0.22250  0.06901  0.15519  0.35117 

            Estimate Std. Error t value Pr(>|t|)   
(Intercept)   1.5376     0.3628   4.238  0.00545 **
lnvote08      0.6086     0.1768   3.442  0.01377 * 
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Residual standard error: 0.2805 on 6 degrees of freedom
Multiple R-squared: 0.6638,     Adjusted R-squared: 0.6078 
F-statistic: 11.85 on 1 and 6 DF,  p-value: 0.01377

Although the coefficient estimate is not so easily interpreted, this model actually does a slightly better job than the simple linear model. (I also test various transformations of the independent variable to get at other nonlinearities, but none of those models improves significantly over this one.) So I use these estimates to get new forecasts of the remaining contests. Here they are:

State Date Forecast
Maine 11-Feb 27.2%
Arizona 28-Feb 11.3%
Michigan 28-Feb 14.2%
Washington 3-Mar 15.8%
Alaska 6-Mar 26.4%
Georgia 6-Mar 8.9%
Idaho 6-Mar 32.0%
Massachusetts 6-Mar 8.4%
North Dakota 6-Mar 29.9%
Ohio 6-Mar 12.2%
Oklahoma 6-Mar 9.7%
Tennessee 6-Mar 13.3%
Vermont 6-Mar 15.4%
Virginia 6-Mar 11.6%
Kansas 10-Mar 20.2%
Alabama 13-Mar 8.6%
Mississippi 13-Mar 10.9%
Illinois 20-Mar 12.5%
Louisiana 24-Mar 13.1%
District of Columbia 3-Apr 16.6%
Maryland 3-Apr 13.8%
Wisconsin 3-Apr 12.0%
Texas 3-Apr 12.5%
Connecticut 24-Apr 10.9%
Delaware 24-Apr 11.2%
New York 24-Apr 14.4%
Pennsylvania 24-Apr 25.1%
Rhode Island 24-Apr 15.1%
Indiana 8-May 16.1%
North Carolina 8-May 15.5%
West Virginia 8-May 12.4%
Nebraska 15-May 22.2%
Oregon 15-May 23.8%
Arkansas 22-May 12.1%
Kentucky 22-May 14.9%
California 5-Jun 12.9%
Montana 5-Jun 17.6%
New Jersey 5-Jun 12.1%
New Mexico 5-Jun 23.2%
South Dakota 5-Jun 25.7%
Utah 26-Jun 8.9%

In general, these new forecasts are lower for Paul in his best states and higher in his worst states. (So yes, his support is less overdispersed this time around, suggesting that his new support is less enthusiastic than his core support – not really surprising.) With the new forecasts, it’s looking unlikely that Paul will win any states outright, although Idaho, North Dakota, and Maine present possibilities.

6 thoughts on “Revisiting My Primary Forecasts

  1. The upside to the caucus states is that it ain’t over until the state conventions. Paul will have a significant advantage at the state convention if his state activists did their job right and got selected to the various state conventions. He is highly likely to pick up more delegates at the various conventions than the polling suggested.

  2. You left out Puerto Rico. It is worth 26 or 28 delegates. Only 800 republicans participated in 2008. The Paul campaign has a team working on winning the whole thing.

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