Senate / South DakotaSouth Dakota Senate 2026 · seat held by Republicans (incumbent running)
Mike Rounds is heavily favored to win South Dakota
Brian Bengs (I)6%Independent
Mike Rounds94%Republican · incumbent
Forecast marginR+9.980%: R+18.0 to R+2.0
Tipping point–chance it decides control
Cook ratingSolid ROct 20
2024 presidentR+29.2nation R+1.5
Polls
Each dot is a poll after adjustment; grey ticks show where it was as publishedDot size shows the weight a poll gets. The line is the model's polling average, with its 80% band. The bar at right is the 80% range of the forecast on election day.
Range of outcomes
Independent margin across simulationsBrian Bengs (I) wins in 6% of simulations (about 1 in 16 for the underdog). Median margin R+10.0.
Chance of winning over time
Daily reruns of the modelEach day is a fresh run of today's model using only the polls that had finished by the day before. Daily runs since Jul 1.
How the forecast is built
Independent races have no partisan baseline, so the forecast leans on polling, with 3 points of extra uncertainty for how independents perform against their polls.
What this race means for control
Because polling errors are correlated, a win here usually comes with wins elsewhere.
Every poll in the model
| Pollster | Field end | Sample | Published | House effect | Adjusted | Weight |
|---|---|---|---|---|---|---|
| Emerson | Oct 20 | 803 LV | R+8.0 | R+0.1 | R+8.3 | 1.06 |
| Quantus | Oct 19 | 633 LV | R+20.0 | R+3.0 | R+17.6 | 0.55 |
| Public Opinion Strategies R internal | Oct 16 | 500 LV | R+17.0 | R+3.7 | R+12.4 | 0.27 |
| Mason-Dixon | Oct 14 | 500 RV | R+19.0 | R+1.9 | R+17.2 | 0.54 |
| Concord D internal | Oct 8 | 400 LV | I+1.0 | D+5.6 | R+6.4 | 0.14 |
| Zenith Research | Sep 27 | 500 LV | R+6.0 | R+0.3 | R+5.7 | 0.50 |
| PPP D internal | Sep 9 | 629 RV | R+3.0 | D+0.2 | R+4.9 | 0.32 |
| Lake Research D internal | Aug 30 | 500 LV | I+7.0 | D+3.5 | I+1.6 | 0.20 |
| Impact Research D internal | Aug 17 | 500 LV | Even | D+0.9 | R+2.9 | 0.23 |