South Dakota state Rep. Kristi Noem won a three-candidate Republican primary in the state’s only Congressional district Tuesday and will face Rep. Stephanie Herseth Sandlin (D) in November.

With about 93 percent of the vote counted, Noem had 42 percent to 35 percent for South Dakota Secretary of State Chris Nelson and 23 percent for state Rep. Blake Curd.

Noem’s win means that South Dakota voters for the first time will choose between two women to represent them in the House.

Noem’s win was impressive in that she entered the race only in February, months after Curd and Nelson. Curd was the best-funded but most politically inexperienced candidate; Nelson began the race as the best-known candidate after two statewide victories, but raised little money.

Republicans didn’t seriously challenge Herseth Sandlin in 2006 and 2008, but party operatives think she’s vulnerable this year in part because of the turbulent political environment and because she hasn’t raised as much campaign money as in previous cycles. The Congresswoman had $452,000 in her re-election account as of mid-May, compared with $754,000 two years ago.

“Like many Democrats representing Republican-leaning districts, Rep. Stephanie Herseth Sandlin is finding that 2010 is a wholly different experience to the campaigns she ran in 2006 and 2008,” the National Republican Congressional Committee said in a memo late Tuesday.

Democratic officials think that Herseth Sandlin, a member of the Blue Dog Coalition of Democrats who promote fiscal restraint, has centrist views that match the district much better than what they say are Noem’s far-right views. They’re also prepared to hit Noem for attacking government spending policies even as her family’s ranch accepts agricultural subsidies.