Modeling the Impact of Vote Share

At RealClearPolitics Sean Trende and David Byler present a handy tool for looking at the effects that voter turnout and what percentage of different demographic segments are carried by each party will have on the outcome of the 2016 elections:

So we’ve developed a tool, embedded below, that allows you to simulate the outcome of the 2016 elections, both in terms of the popular vote and the Electoral College. You can read the complete description of our methodology here. In the interest of space and readability, we’ll just give a general overview in this article.

We’d like first, however, to emphasize two things about the tool that are important to keep in mind if it is to be used appropriately. First, there is some estimation involved here, both within the datasets upon which we draw and in the way in which we adjust for differences in datasets.

Because of this, we envision this as more of a heuristic device than a literal tool. In other words, if you put in an outcome and the Democrats win the Electoral College, but that win is dependent upon a state where the Democrat wins by 0.1 percent, you shouldn’t become convinced that Democrats would actually win with the outcome that you input.

Second – and this gets into our explanation of how the model works – we assume “uniform swing” across states. In other words, if the non-Hispanic white share of the electorate increases in the model by a point, it does so in every state. In reality, however, these swings will likely not be uniform. While we have some ideas about where the white vote might improve more for Republicans than the national margin would indicate (Iowa, for example), as well as for Democrats (perhaps Arkansas, if Hillary Clinton is the nominee), there’s simply no way to incorporate that objectively into a model.

In any event, the key to operating the tool is the dashboard on top. It defaults to 2012 levels of turnout and support, by racial/ethnic group. Note that we’ve combined “Asian” and “Other,” which was necessitated by the different datasets we’ve used. You’ll also notice that the Democratic lead using the default numbers is about six-tenths of a point larger than the actual result was in 2012; this is demographic change at work.

Mark my words: this is going to be an election that hinges on turnout. Whoever the candidates, the party with the more highly motivated voters will win.

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