The Election Wonk's Guide to Tuesday's Governor Races

Virginia and New Jersey—two states with a combined population of about 17 million—are voting today in the largest American elections since November 2016. Both states are choosing new governors and electing numerous state and local officials. So it’s worth asking: Who’s going to win? And what do those wins mean in the Trump era? I’ll break down each question for each state.

Virginia: Where We Are and Where We’re Heading

According to the average of current polls, Democrat Ralph Northam is the favorite to win Tuesday’s contest. But it’s not an open-and-shut case.

The RealClearPolitics average puts Northam ahead of Republican Ed Gillespie by 3.3 points, but polls aren’t perfect.

This table shows the final margin in the RealClearPolitics average for a number of statewide races in Virginia over the last decade. A quick scan shows that neither party consistently outperforms the other in the state. Republicans outperformed their final average in four of the nine races, and Democrats outperformed their polls in the other five. And an average polling error from this set of races would ( depending on who it favors) turn a 3.3 point Northam edge into a functionally tied race or an almost seven-point win.

This metric for error isn’t perfect – presidential, Senate and off-year gubernatorial elections aren’t the same. Pollsters face different challenges in each of them, and the specific conditions of each race (e.g., how many polls were fielded in the days leading up to the election) will affect the accuracy of any poll average.