Super Tuesday: What does it mean for the Democratic Primary? [Greg Laden's Blog]

As you know, I developed a simple model for projecting future primary outcomes in the Democratic party. This model is based on the ethnic mix in each state, among Democratic Party voters. The model attributes a likely voting choice to theoretical primary goers or causers based on previous behavior by ethnicity. Originally I made two models, one using numbers that the Clinton campaign was banking on, and one using numbers that the Sanders campaign was banking on.

The results of the Super Tuesday primaries demonstrated that the Sanders-favoring model does not predict primary outcomes. Those same results showed that the Clinton-favoring model worked better. But the numbers also indicated that the Clinton favoring model estimates Clinton’s ultimate delegate take somewhat inaccurately.

I adjusted the model parameter so the model now matches reality for a subset of the primaries that have already happened to within five percent. The model still slightly favors Clinton, but not by much. The subset of primaries includes only the US states (not territories, where I don’t expect the ethnic mix approach to work at all) and excludes states with a strong favorite son effect. This therefore excludes New Hampshire and Vermont. Due to oddities in the Texas delegate system, the adjustment was also made by excluding Texas, though the model results for Texas match very well proportionately.

(Note: Using only the subset of states, the model predicts previously held primaries and caucuses to within less than two tenths of a percent).

The new model now only has one version, which as noted matches primaries so far very well. While there is a somewhat southern bias in the set of primaries that have been carried out so far, that bias is probably not important. I have a fairly high level of confidence in the model.

The result is best seen in this graphic, which shows the cumulative delegate count of committed delegates in US states. So this excludes non-committed delegates (known as “Super Delegates”) and it excludes territories and other non-states (but it does include DC, because DC is like a state).

Assuming a large proportion of the Democratic Party’s uncommitted delegates support Clinton, Clinton will probably achieve the necessary number of delegates to lock the nomination either on the 19th of April with the New York primary, or on the 26th of April, with the Maryland, Connecticut, Delaware, Pennsylvania and Rhode Island primaries.

There are two phases of primaries coming up. First we have a series of weeks with only one or two primaries happening at once, with a total of 300 committed delegates (130 from Michigan). Then we have what is effectively Return of Super Tuesday, with 691 committed delegates, including Florida with 214. For Sanders to regain traction, he has to do well in some of these big states. In particular, Sanders has to outperform the model in Michigan, Florida, Illinois and possibly North Carolina and Ohio.

When we look at many of these states, the model seems to fit very well with the available polling data, except in cases where the polls suggest a stronger outcome for Clinton. The following table compares the model projections with estimates of the delegate split based on polls. All delegates are assumed to be awarded (among the committed delegates only) and the polling data is not very dense and in some cases not too recent, so this is a very rough estimate.

Prior to Super Tuesday, the then-current version of this model projected results that conformed closely with polls. For most states, the outcome of the actual voting matched the projections and the polls pretty well, except in a couple of places. Now, the refined model matches polling data even more closely, but the polling data is not necessarily to be trusted because there has not been enough polling. (I avoided comparisons with really old polls which are entirely useless).

Clinton’s path to the nomination is clear. Sanders’ path to the nomination requires something to change, and to change dramatically and quickly.