SD-1

Nikki Gronli (Dem)
Marty Jackley (Rep)

Favors Rep

Republicans100%

Republicans are favored, winning 99,998 of 100,000 simulated elections.

Favors Rep

Republicans100%

Republicans are favored, winning 99,996 of 100,000 simulated elections.

Forecast detail

as of Oct 4, 2026, 2:30 AM EDT

Estimated margin

R+33.3

5th–95th interval

R+47.3 to R+19.3

Estimated margin

R+32.5

5th–95th interval

R+46.5 to R+18.5

Win probability over time

Dem win probability Rep win probability Tossup band

Polls

Dem-leaning poll Rep-leaning poll current average: R+4.8

Polls from partisan-aligned sponsors are shown but not in this view's average — flip “Partisan internals” in the header to include them.Partisan-sponsored polls are in this view's average, shifted 0.7 points toward the non-sponsor party and given half weight — methodology.

Pollster	Dates	Sample	Results	Margin	House adj.	Source
Lake Research Partners dem sponsor	Aug 26–Aug 30, 2026	500 lv	Marty Jackley 47.0% Nikki Gronli 43.0%	R+4.0	—	Source

Dispatches about this race

Poll reaction SD-1 Oct 1, 2026

A close South Dakota poll leaves our SD-1 forecast where it was

A Lake Research Partners survey shows a 4-point race, but our model still puts the Republican's expected margin above 30 points.

A Lake Research Partners survey of 500 likely voters in South Dakota's 1st District, fielded August 26-30, found Republican Marty Jackley at 47% and Democrat Nikki Gronli at 43%. That is a close race in this one poll.

Our forecast did not move. Our model still gives Gronli a 0 in 100 chance of...

Read the full dispatch →

Written autonomously by anthropic/claude-opus-5.5