Monmouth University Polling Institute
Graded against the actual result across 110 races (from 172 polls, through 2021).
Head-to-head vs the VotePredictor model
The fair, apples-to-apples test: on the 109 races Monmouth University Polling Institute actually polled, how its final poll's margin compared to what the VotePredictor model predicted for those same races.
| Model | Avg miss (pts) | Called right |
|---|---|---|
| Monmouth University Polling Institute | 5.22 | 70% |
| VotePredictor | 4.21 | 76% |
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 (109)
Each race Monmouth University Polling Institute 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
Lower is better. Time to election runs right (election week) to left (~2 months out).
By the numbers
| Time to election | Polls | Avg miss | vs field | Called right |
|---|---|---|---|---|
| ≤1 wk | 15 | 3.91 | -0.37 | 80% |
| 1–3 wk | 63 | 5.55 | +0.48 | 62% |
| 3–6 wk | 59 | 6.02 | +0.28 | 68% |
| 6–9 wk | 35 | 4.98 | -1.17 | 74% |
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?
| Year | Polls | Avg miss | Lean (house effect) |
|---|---|---|---|
| 2005 | 3 | 2.5 | R+2.5 |
| 2006 | 3 | 14.0 | R+14.0 |
| 2008 | 8 | 4.6 | R+0.1 |
| 2009 | 5 | 3.4 | D+1.6 |
| 2010 | 15 | 3.9 | R+0.7 |
| 2012 | 6 | 4.0 | R+4.0 |
| 2013 | 6 | 2.5 | D+1.6 |
| 2014 | 18 | 3.9 | D+3.4 |
| 2016 | 52 | 6.5 | D+5.6 |
| 2017 | 6 | 3.8 | R+3.8 |
| 2018 | 20 | 5.3 | R+3.4 |
| 2020 | 26 | 6.6 | D+5.6 |
| 2021 | 4 | 6.6 | D+6.6 |
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.