Ned Foley and Charles Stewart APSA paper:

We conduct statistical analysis of a phenomenon recently identified by Foley (2013), the rise in the number of votes counted after Election Day (“overtime votes”) and the growing tendency of these votes to disproportionately favor Democrats in presidential elections (the “blue shift.”) We provide a historical description of these two time series, from 1948 to 2012, and establish that the timing of the persistent growth in the blue-shifted overtime vote began with the 2004 election. While some of the interstate variability in these time series is accounted for by regional factors (e.g., a lag in news travelling to New York), changes in the time series are broadly consistent with changes in electoral practices, especially in recent years.

We perform statistical analysis to understand better interstate variability in the overtime vote and the blue shift in the 2012 presidential election. We discover that variation in the size of the overtime vote is associated with the number of provisional ballots, but not the number of absentee/mail ballots; variation in the relative size of the blue shift is positively associated with the number of provisional ballots and with the Democratic partisanship of the states. We also perform an analysis of the overtime vote in seven statewide contests in Virginia, using that state’s change log as evidence. We find a tendency of provisional ballots to persistently favor Democrats in these races, whereas other sources of votes accounted for after Election Day do not persistently favor Democrats in that state.

We conclude the paper by suggesting how the analysis offered here might be expanded in future work.