We've heard that as running mates, Rob Portman of Ohio and Marco Rubio of Florida could help Mitt Romney in their battleground home states—but statistics wiz Nate Silver isn't so sure. In the New York Times, he evaluates the performances of presidential tickets in the VP nominee's home states, dating back to 1920. Despite a number of caveats, he finds that the much-vaunted home-state effect "is normally quite modest—perhaps two or three percentage points on average."
In order to make his assessment, Silver compares a ticket's performance in the VP's home state to its performance nationally, among a host of other factors. In recent years, he notes, the home-state advantage actually seems a little bigger than in the past—an average of some 4 percentage points since 1984. But in the end, the effect probably doesn't "outweigh the other strengths and weaknesses that a vice presidential candidate could potentially impart onto the ticket."