Using State Poll Performance Metrics to Verify National Support

Last week in the comment section to one of my articles at Wizbang, reader Andrew Byler made an important observation regarding the over/underperformance of state polls. I think it got lost by most readers, so I am posting today’s article on that subject.

The more observant readers have noticed that the election depends more heavily on state results than the national tally, so they have repeatedly asked about what the state polls say. There is a range of opinion coming out of those polls, but one thing that should be observed, is that there is a clear relationship between the state and national performance. For example, in the state of Ohio, it has long been said that no Republican can win without it. That is the case, it turns out, because Ohio tends to track relatively close to national performance; if a republican does poorly in Ohio, he will likely do poorly across the nation. Over the course of election history, most states have demonstrated a tendency to favor the republican or democrat candidate, and by a certain range of support. This allows us to use the state polls to test the veracity of the national polls, and vice versa.

Let’s have a look at a few states to see how this plays out:

Let’s start with California. RCP’s average shows Obama ahead by 14.5 points in California. RCP also says Obama is ahead 7.1 points nationally. Looking at California, we see that on average, California favors the democrat candidate by an average of 4.0 points more than the national average, based on past election results. Accordingly, California’s poll numbers suggest that Obama’s real lead nationally is 11.1 points;

The next state is Texas. RCP’s average shows McCain ahead by 12.7 points in Texas. On average, Texas favors the republican by 7.0 points more than the national average, suggesting that McCain is leading the race, by 5.7 points.

Next up is New York. RCP’s average shows Obama ahead by 18.0 points in New York. On average, New York favors the democrat by 8.8 points more than the national average, suggesting that Obama is leading the race nationally by 9.2 points.

Next up is Alabama. RCP’s average shows McCain ahead by 23.8 points in Alabama. On average, Alabama favors the republican by 7.9 points more than the national average, suggesting that McCain has the national lead, by 15.9 points.

Next up is Florida. RCP’s average shows Obama up by 3.8 points in Florida. On average, Florida favors the republican by 2.8 points more than the national average, suggesting that Obama is leading the race nationally by 6.6 points.

Next up is Tennessee. RCP’s average shows McCain up by 15.7 points in Tennessee. On average, Tennessee favors the republican by 3.2 points more than the national average, suggesting that McCain is leading the race nationally by 12.5 points.

As you can see, there is no clear consensus from these results. Taken altogether, the 50 states project an Obama lead of 0.99 points right now. When the range of skewing is considered, the range could be anywhere nationally from Obama by 3.05 to McCain by 4.71 points.

Once again, the indications from the math are that the race is both close and fluid.