Our role model’s message for the Virginia gubernatorial race
TIT RESULTS Virginia’s race for governor on Nov. 2 will “set the tone” for next year’s midterm elections. That’s what Terry McAuliffe, the state’s former Democratic governor, said as he launched a campaign for the vote last Friday. If so, the party is in trouble. President Joe Biden won the state by ten percentage points last year, but Mr McAuliffe is now just two points ahead of his Republican opponent, Glenn Youngkin, according to a statistical model built by The Economist. This gap is small enough that Mr. Youngkin is closing at the last minute.
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Our model aggregates published polls and attempts several modest corrections to the underlying data. First, we remove any uniform bias from each survey company. These may arise from the methods of data collection or processing or, in rarer cases, from the ideological bias of the polling station. We then subtract any systematic differences between pollsters who try to make sure they have representative shares of Democrats, Republicans and Independents and those who don’t. This helps to control for the tendency of unweighted party data to rebound more than party-weighted polls; in some cases it also removes an extra layer of bias. Finally, we use the model to fit a trend line through all the fitted points. This method gave a closer prediction of the recent California recall election than most other public poll data averages.
If the election were held today, our model suggests that Mr. McAuliffe would beat Mr. Youngkin by about two percentage points. This shouldn’t give Democrats any comfort. Our model also finds a lot of uncertainties in the poll data: it only gives the former governor about two in three (67%) chances of winning the race. Even a modest survey error could derail the aggregate. In 2017, when current Democratic state governor Ralph Northam won the job, the Virginia poll average underestimated its margin by six percentage points.
Win or lose, the tone the mid-term election sets may be bad for Democrats. The White House party typically loses both the following elections for governor of Virginia and the seats in the national House and Senate elections the following year. And a close relationship exists between the swing against the ruling party in these gubernatorial contests and in the nationwide House vote. With Mr Biden’s net approval rating underwater and a trend against Democrats in generic congressional polls, even a five or six point margin for Mr McAuliffe on November 2 would portend a loss to mid-term.
This article appeared in the United States section of the print edition under the title “Down to the wire”