From FiveThirtyEight:

The Washington Post reports that Democrats are dominating early voting in Nevada. Business Insider notes that Latino early voting in Florida is up 99 percent over 2012’s figures, suggesting a strong showing for Hillary Clinton there. But Fox News warns that the early voting numbers indicate a very close race. These divergent views serve as an important reminder that as popular as early voting is, it doesn’t actually tell us very much about who’s going to win the election.

Let’s look at states that had early voting in 2012 and reported the party registration of early voters (using the invaluable data collection provided by Michael McDonald, a political science professor at the University of Florida). There were only 12 such states that year. For each state, I calculated the Democratic share of the two-party early vote and the Democratic share of the two-party total vote. (So we’re excluding third-party candidates from both numbers.)

The former very weakly predicts the latter. Yes, the relationship is positive, but it’s pretty noisy.1 In other words, knowing how a party is doing in early voting doesn’t tell you much about how it will do once all the votes are counted.

Indeed, if you were relying on early votes to forecast what was going to happen on Election Day in 2012, you’d get wildly misleading results. Democrats maintained substantial leads among early voters in North Carolina, Louisiana and West Virginia, and were trailing by a relatively narrow margin in Oklahoma, but still lost those states when all the votes were counted. Republicans won early voters in Pennsylvania and Colorado but lost the final tallies there. Maryland was a safely Democratic state in 2012, but the 75 percent of the early vote …

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