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2026 forecast · South Dakota Senate

Mike Rounds is all but certain to win South Dakota's Senate seat.

Brian Bengs vs Mike Rounds. The model has Rounds ahead by 20.0 points, winning 100 percent of 2,000 simulated elections.

Safe RModel R +20.0Polls R +18.8Updated October 22, 2026
Brian Bengs
Independent
40.0%
153,493 projected votes
Mike Rounds
Republican
60.0%
230,229 projected votes
100%Rounds
0%Bengs
Rounds all but certainEach square is one simulated election night, Rounds wins about 100 of 100
RatingSafe R100% chance for Rounds
Model marginR +20.0Polls R +18.8
80 percent rangeR +10.8 to R +28.42,000 simulations
Projected votes383,722Rounds 60.0%

The county map

Four ways to read the state: margin, shift from 2024, vote bubbles and turnout

South Dakota Senate by county

Aurora CountyBeadle CountyBennett CountyBon Homme CountyBrookings CountyBrown CountyBrule CountyBuffalo CountyButte CountyCampbell CountyCharles Mix CountyClark CountyClay CountyCodington CountyCorson CountyCuster CountyDavison CountyDay CountyDeuel CountyDewey CountyDouglas CountyEdmunds CountyFall River CountyFaulk CountyGrant CountyGregory CountyHaakon CountyHamlin CountyHand CountyHanson CountyHarding CountyHughes CountyHutchinson CountyHyde CountyJackson CountyJerauld CountyJones CountyKingsbury CountyLake CountyLawrence CountyLincoln CountyLyman CountyMcCook CountyMcPherson CountyMarshall CountyMeade CountyMellette CountyMiner CountyMinnehaha CountyMoody CountyOglala Lakota CountyPennington CountyPerkins CountyPotter CountyRoberts CountySanborn CountySpink CountyStanley CountySully CountyTodd CountyTripp CountyTurner CountyUnion CountyWalworth CountyYankton CountyZiebach CountyMinnehahaPenningtonLincolnBrownBrookingsLawrenceMeadeCodingtonYanktonDavisonHughesUnion
D +40R +40Click a county to zoom · arrow keys step through counties by size
Where the margin is won
Oglala Lakota County: Bengs +2,431Todd County: Bengs +1,374Clay County: Bengs +761Dewey County: Bengs +373Buffalo County: Bengs +153Minnehaha County: Bengs +94Ziebach County: Bengs +79Corson County: Bengs +48Pennington County: Rounds +10,066Lincoln County: Rounds +7,627Meade County: Rounds +5,390Codington County: Rounds +4,439Lawrence County: Rounds +3,492Brown County: Rounds +2,811Hughes County: Rounds +2,704Davison County: Rounds +2,676Union County: Rounds +2,291Butte County: Rounds +2,242Brookings County: Rounds +2,170Beadle County: Rounds +2,129Yankton County: Rounds +1,916Hutchinson County: Rounds +1,865Custer County: Rounds +1,831Turner County: Rounds +1,570Fall River County: Rounds +1,467Tripp County: Rounds +1,376Hamlin County: Rounds +1,351Walworth County: Rounds +1,165Lake County: Rounds +1,163Grant County: Rounds +1,125Douglas County: Rounds +1,031Gregory County: Rounds +1,015Bon Homme County: Rounds +1,006McCook County: Rounds +915Charles Mix County: Rounds +899Perkins County: Rounds +885Kingsbury County: Rounds +856Edmunds County: Rounds +841Hand County: Rounds +787Spink County: Rounds +783Deuel County: Rounds +759Haakon County: Rounds +753Clark County: Rounds +743Hanson County: Rounds +731Potter County: Rounds +728Stanley County: Rounds +714McPherson County: Rounds +710Brule County: Rounds +661Faulk County: Rounds +591Harding County: Rounds +516Day County: Rounds +505Campbell County: Rounds +460Sully County: Rounds +450Sanborn County: Rounds +438Aurora County: Rounds +428Moody County: Rounds +412Lyman County: Rounds +381Roberts County: Rounds +334Marshall County: Rounds +323Hyde County: Rounds +315Jones County: Rounds +309Jerauld County: Rounds +308Miner County: Rounds +306Jackson County: Rounds +302Bennett County: Rounds +198Mellette County: Rounds +94
Bengs +5,313 net votes from 8 countiesStatewide R +20.6, a 79,040 vote marginRounds +84,353 net votes from 58 counties

Vote share

Each candidate's projected share and the range of 80 percent of simulations

Brian BengsIND · 0% to win
40.0%
Mike RoundsRepublican · 100% to win
60.0%

Scale runs from 25 to 75 percent. The dot is the forecast, the band is the 80 percent range and the brighter tick marks 50 percent.

Projected statewide vote

383,722 votes
CandidateVotesShare
Mike Rounds R230,22960.0%
Brian Bengs IND153,49340.0%
Total383,722100%

Each candidate's expected vote in the On Point simulation, at the forecast's projected turnout.

Every simulated outcome

2,000 sims
D +25.1: 1 simulationsD +23.3: 0 simulationsD +21.5: 0 simulationsD +19.7: 0 simulationsD +17.9: 0 simulationsD +16.1: 0 simulationsD +14.3: 0 simulationsD +12.5: 0 simulationsD +10.7: 0 simulationsD +8.9: 1 simulationsD +7.1: 1 simulationsD +5.3: 2 simulationsD +3.5: 2 simulationsD +1.7: 3 simulationsR +0.1: 2 simulationsR +1.9: 9 simulationsR +3.7: 16 simulationsR +5.5: 25 simulationsR +7.3: 35 simulationsR +9.1: 67 simulationsR +10.9: 85 simulationsR +12.7: 93 simulationsR +14.5: 144 simulationsR +16.3: 166 simulationsR +18.1: 187 simulationsR +19.9: 210 simulationsR +21.7: 229 simulationsR +23.5: 181 simulationsR +25.3: 183 simulationsR +27.1: 132 simulationsR +28.9: 95 simulationsR +30.7: 44 simulationsR +32.5: 38 simulationsR +34.3: 18 simulationsR +36.1: 20 simulationsR +37.9: 3 simulationsR +39.7: 4 simulationsR +41.5: 2 simulationsR +43.3: 1 simulationsR +45.1: 1 simulationsD +26.0R +46.0

80 percent of simulations fall between R +10.8 and R +28.4. Negative margins are Democratic wins.

The trend

Each side's chance of winning over the forecast's recent updates

0%25%50%75%100%0% Bengs100% Rounds30 updates agoToday

Polling

Every poll in the average, and how the model reads it

The South Dakota Senate polling average
30%35%40%45%50%55%60%AugSepOct38.3Bengs48.0Rounds
The line is the On Point average: a robust LOWESS fit through the polls, weighted by recency, sample, voter screen and pollster grade, refit three times so outliers count for lessDot size is each poll's weight todayHover or use the arrow keys to read any day
What moves the average today
Zenith Research for Bengs (I)Sep 28 · 600 RV · NR18%Rounds +6.0
Zenith ResearchSep 27 · 500 LV · NR17%Rounds +6.0
Public Opinion Strategies for Rounds (R)Oct 16 · 500 LV · NR16%Rounds +17.0
Concord Public Opinion Partners (D)Oct 8 · 400 LV · NR15%Bengs +1.0
Quantus InsightsOct 18 · 630 LV · Gold14%Rounds +20.7
Lake Research Partners (D)Aug 30 · 500 LV · NR13%Bengs +7.0
Every other poll together: 6.7%

This is the same On Point polling average as the full average page. The forecast reads the polls through its own Election Day projection, shown as the On Point average in the table below, and blends it with partisan lean and fundamentals.

Polls of the race

Full average
PollsterSampleAgeMargin
On Point averageWeighted averageR +18.8
Public Opinion Strategies for Rounds (R)500 LV0dR +17.037 to 54
Quantus Insights630 LV0dR +20.736.5 to 57.2
Mason-Dixon for South Dakota News Watch and USD Chiesman Center500 LV1dR +19.037 to 56
Concord Public Opinion Partners (D)400 LV7dD +1.043 to 42
Zenith Research500 LV18dR +6.038 to 44
Public Policy Polling (D)629 RV36dR +3.042 to 45
Lake Research Partners (D)500 LV46dD +7.051 to 44
Impact Research (D)Lean D500 LV59dEven44 to 44
Public Opinion Strategies (R)500 LV98dR +23.033 to 56

Each margin is the poll as the pollster published it. The forecast counts every poll after its house effect and the undecided split, which is what the trail above shows; hover a margin for the counted value. Lean R and Lean D mark partisan leaning firms.

Model margin
Rounds +20.0
Chance of winning
Brian Bengs0%
Mike Rounds100%
Simulated vote
Brian Bengs40.0%
Mike Rounds60.0%
How the model gets there
Partisan leanR +29.9
FundamentalsR +20.5
With pollsR +19.4
Early vote turnoutR +0.6
With early voteR +20.0

Read from 31,562 ballots cast so far in South Dakota, against the party mix the forecast expected of them, with similar states and primary turnout. Early vote tracker

Who has endorsed

1 public endorsements in this race, each with where it was reported.

Mike Rounds1
Every endorsement on Watchdog

How we got here

From the state's partisan lean to the forecast, one stage at a time

D +36R +36Partisan leanthe state's baselineR +29.9Fundamentalsapproval, economy, candidatesR +20.5With pollsaverage R +18.8R +19.4With early voteturnout so farR +20.0

Who votes for whom

Estimated vote by group from the model's simulated electorate

Estimated vote by group

model crosstabs
GroupShareBengsRounds
GenderMen48%40.159.9
Women52%48.551.5
Age18 to 2912%49.950.1
30 to 4421%45.055.0
45 to 6433%41.958.1
65+34%44.755.3
RaceWhite89%40.859.2
Black2%87.912.1
Latino2%61.438.6
Asian and other8%73.326.7
Race and genderWhite men42%35.364.7
White women47%45.754.3
Latino men1%59.440.6
Latino women1%63.536.5
All other races8%73.326.7

Every county

The projected vote in each county, largest first

Projected vote by county

66 counties
CountyBengsRoundsOtherTotalMargin
Statewide152,342231,3821383,722R +20.6
Minnehaha County41,57041,476083,046D +0.2
Pennington County20,04930,115050,164R +20.0
Lincoln County11,87819,505031,383R +24.2
Brown County6,3439,154015,497R +18.0
Brookings County5,8788,048013,926R +15.7
Lawrence County4,9988,490013,488R +25.8
Meade County3,8419,231013,072R +41.2
Codington County3,8028,241012,043R +36.8
Yankton County3,9605,87609,836R +19.6
Davison County2,7145,39008,104R +33.1
Hughes County2,5935,29707,890R +34.2
Union County2,6514,94207,593R +30.2
Beadle County2,1864,31506,501R +32.9
Clay County3,1992,43805,637D +13.4
Custer County1,7353,56605,301R +34.6
Lake County2,0633,22605,289R +21.9
Butte County1,1403,38204,522R +49.5
Turner County1,2462,81604,062R +38.7
Fall River County1,1852,65203,837R +38.2
Roberts County1,7332,06703,800R +8.6
Hutchinson County7482,61303,361R +55.5
Charles Mix County1,2292,12803,357R +26.9
Grant County1,1042,22903,333R +33.9
Oglala Lakota County2,84541403,259D +74.4
Spink County1,0301,81302,843R +27.5
Hamlin County7382,08902,824R +47.7
Moody County1,2041,61602,820R +14.6
Bon Homme County8951,90102,796R +36.0
McCook County8791,79402,673R +34.1
Day County1,0611,56602,627R +19.2
Kingsbury County8571,71302,570R +33.4
Tripp County5241,90002,424R +56.8
Walworth County5381,70302,241R +52.0
Brule County7811,44202,223R +29.6
Todd County1,79642202,218D +62.1
Deuel County6561,41502,071R +36.6
Gregory County5231,53802,061R +49.2
Marshall County8141,13701,951R +16.4
Edmunds County4891,33001,819R +46.3
Hanson County4861,21701,703R +43.0
Dewey County1,02665301,679D +22.0
Clark County4631,20601,669R +44.7
Hand County3891,17601,565R +50.7
Stanley County4121,12601,538R +46.5
Douglas County2351,26601,501R +68.6
Perkins County2831,16801,451R +60.8
Lyman County49287301,365R +28.0
Aurora County40383101,234R +34.8
Potter County22395111,175R +61.9
McPherson County23094001,170R +60.5
Sanborn County31174901,060R +41.4
Corson County55150301,054D +4.2
Miner County36967501,044R +29.8
Bennett County42262001,042R +18.8
Faulk County20879901,007R +58.4
Haakon County12587801,003R +75.0
Jackson County3396410980R +30.7
Jerauld County2895970886R +34.7
Sully County1766260802R +55.5
Ziebach County4073280735D +10.4
Campbell County1375970734R +62.7
Mellette County2903840674R +14.4
Harding County765920668R +77.8
Hyde County1494640613R +51.7
Jones County833920475R +64.7
Buffalo County2931400433D +35.6

Projected 2026 votes from the On Point simulation: each county's expected turnout times its simulated vote share. Totals may differ from the race total by rounding.

Methodology
Every county is rebuilt by simulating voters going to the polls, 2,000 times, from On Point Polling survey data, past results, and the polling average. How the model works.