Chance of Democrats or Republicans winning a House majority over time
Projected House Partisan Control
Distribution of House race control are generated based on 20k simulations.
Chances of a Republican win in the closest House races
Shown below are the probabilities of a Republican victory in Senate races within 67% probability.
Probabilities in Republican-held districts predicted to flip
These districts are predicted to be won by a Democrat but are represented by a Republican.
Probabilities in Democratic-held districts predicted to flip
These districts are predicted to be won by a Republican but are represented by a Democrat.
How accurate are our predictions?+−
Our model depends primarily on polls to predict vote outcomes. Past polling error informs our modelling of the uncertainty of our predictions. We model the probabilities using the beta, weibull, and logistic distributions. The Senate partisan control vote and probability is estimated using 10,000 Monte Carlo simulations.
In addition to polls, which we weight as 3/5th of our predictions in our House forecast, we incorporate a k-nearest neighbors algorithm to discern what polls tell us about states with little data.
Credit to Daniel Donner of Daily Kos for shapefiles of the population-adjusted map.