Betting Odds Suggest Republicans Likely to Reclaim Congress, Contradicting 538 Forecast

Betting odds contradict election forecaster FiveThirtyEight’s prediction that Republicans might not reclaim both chambers of Congress come November 8.

The difference between polling-based forecast models and betting market data is notable. The official forecast from FiveThirtyEight gives Republicans less than a 50 percent chance to reclaim both chambers, while members of the public who have wagered money on the midterm elections place the odds at a 75 percent chance.

Political betting markets are a notable source of data because they run on monetary bets, not solicited opinions given to pollsters that use statistical models that have proved to be wrong in the past.

The odds that Republicans will reclaim Congress are pegged at 75 percent, according to PredictIt. Meanwhile, the betting odds suggest bettors believe there is only a 25 percent chance Democrats will keep the Senate and lose the House.

According to FiveThirtyEight, Republicans only have a 47 in 100 chance of reclaiming both the House and the Senate.  Pollsters also estimate Democrats have a 34 in 100 chance of retaining the Senate and losing the House.

FiveThirtyEight’s prediction is based on a “model that simulates the election 40,000 times to see which party wins the Senate most often,” its website states. “This sample of 100 outcomes gives you an idea of the range of scenarios the model considers possible.”

FiveThirtyEight’s model says Republicans have only a 48 in 100 chance of retaking the Senate. Democrats are favored by a 52 in 100 chance of keeping it.

Republicans have an 82 in 100 chance of reclaiming the House, according to FiveThirtyEight, while Democrats have just an 18 in 100 chance of keeping it.

Follow Wendell Husebø on Twitter @WendellHusebø. He is the author of Politics of Slave Morality.