COYNTOSSby @achasecoyne

Updated September 29, 2026 · model inputs through September 27, 2026

South Dakota Senate Forecast

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Independent Brian Bengs is challenging Senator Mike Rounds after previously running statewide as a Democrat. South Dakota’s Republican lean is formidable, but Bengs’s independent label asks whether voters will separate a candidate from the national party ledger.

Forecast summary

Model margin
R+16.84
Rating
Safe R
Polling average
R+6.45
Fundamentals
R+25.06
Matchup
Brian Bengs vs. Mike Rounds

FORECAST HISTORY

Model margin over time

Forecast history will appear after the first recorded model release.

No candidate win probabilities have been published from a frozen, label-verified simulation run yet.

MODEL BREAKDOWN

How the forecast is built

The polling average and fundamentals are blended at their published weights.

Polling average — — · —
Fundamentals — — · —
Projected margin — Published model output
Polling Fundamentals

Margins are D-minus-R points. Candidate strength is included in fundamentals; its separate score is not published. Values are rounded to two decimals.

POLLING INPUTS

Polls behind the average

Polling average
R+6.45

Field dates Pollster Sample Results
Fielded Sep 8–Sep 9, 2026Public Policy Polling (I)629 RVD Brian Bengs 42% · R Mike Rounds 45% · O Undecided 13%
Fielded Aug 13–Aug 17, 2026Impact Research (I)500 LVD Brian Bengs 44% · R Mike Rounds 44%
Fielded Jul 6–Jul 9, 2026Public Opinion Strategies500 LVD Brian Bengs 33% · R Mike Rounds 56%
Fielded May 29–May 30, 2026PPP726 RVD Brian Bengs 40% · R Mike Rounds 44%

The published average comes directly from the workbook. Polls are not equally weighted, and the browser does not recompute the forecast.

The published average comes directly from the workbook. Polls are not equally weighted, and the browser does not recompute the forecast.

See all Senate races