Why did Hillary win the South Dakota primary?

[Nichlemn]

Obama won all the surrounding states and was thought to be a favourite, but Clinton won by 10 points. Is there anything unique to South Dakota or was this an artifact of the campaign, perhaps a sympathy vote for the almost-sure loser?

[Californian Tony]

Maybe Republicans who wanted to troll... is SD an open primary?

[bedstuy]

A few things.

Iowa, Minnesota, Wyoming and North Dakota are caucus states.  Nebraska has a few black people.  Montana is in the mold of the Western states that Obama won and the campaign put more resources in Montana because it was a potential swing state.

[Clinton 2016]

The clintons hit this state hard and poured money into my state because they thought it would be the "game breaker" in the end

[Landslide Lyndon]

The clintons hit this state hard and poured money into my state because they thought it would be the "game breaker" in the end

That.
Obama also had already shifted into general election mode and spent most of his time campaigning in states like Michigan, Missouri and Wisconsin.

[Mr. Morden]

Didn't Nate Silver have state-by-state predictions for every primary in 2008, based purely on the demography of each state?  What did his formula say for South Dakota?

[paulsonj72]

Maybe Republicans who wanted to troll... is SD an open primary?

No it's not. When you register to vote you register by party. I used to live just across the border in South Dakota from MN and when I registered to vote I had to put a party down.

[TDAS04]

I was at the last Hillary rally in 2008; I got to see her, Bill, and Chelsea when they stopped in Sioux Falls the night before the primaries were over.

Nate Silver actually predicted an Obama victory in the SD primary, reasoning that SD whites were primarily of English, German, and Scandinavian ancestry; these whites tend to be more socially liberal then some other groups of whites.

While Silver is more accurate of a predictor than anyone else, he did not call this one correctly.  I believe that Hillary won SD by simply taking the time to campaign here, and it pays off in a small state.  Certainly, South Dakota Democrats did not have the same hostility to Obama as Democrats in Kentucky or West Virginia.