Mellman Group

Head-to-head vs the VotePredictor model

The fair, apples-to-apples test: on the 37 races Mellman Group actually polled, how its final poll's margin compared to what the VotePredictor model predicted for those same races.

VotePredictor aggregates all the pollsters, so it's expected to beat any single one on margin — that's the value of averaging. The honest comparison among forecasters is on the combined board.

Every race (43)

Each race Mellman Group polled, scored on its final poll — the call right before the vote — against the actual Dem−Rep result. Click a race for its full detail.

Accuracy by time to election

By the numbers

vs field is this pollster's average miss minus all pollsters' at the same lead time — green beats the field, redtrails it. Our historical polls reach ~2 months out; earlier polling isn't in the record.

Track record by cycle — getting better?

Do we credit a pollster for fixing its bias? Each cycle, the model re-estimates every pollster's lean from all its earlier polls (walk-forward) and subtracts it before using the poll. We tested weighting recent cycles more — it doesn't help: a pollster's lean in one cycle barely predicts the next (correlation 0.28), so the swings above are mostly noise, and averaging over more history beats chasing the latest cycle. The all-time estimate we use came out within ~0.5% of the best option.