Mortenson's political action committee $48,271 spent help some of the incumbents and other candidates who Odenbach against it.

Mortenson attributed the incumbent's losses primarily to the historically low voter turnout of 17%, which he believes creates an environment in which a motivated faction can mobilize enough voters to influence a primary.

Pipelines and property taxes

Odenbach said the challengers won because they recruited quality candidates, did good groundwork and got the right message across.

Much of this messaging, particularly in eastern South Dakota, capitalized on opposition to Summit Carbon Solutions’ proposal to billion-dollar pipeline projectIt would capture carbon dioxide from ethanol plants in South Dakota and other states and send it through an underground pipeline for storage in North Dakota, passing farms, ranches and other private property along the way.

Incumbent Republican lawmakers suffer losses as pipelines and property rights come to the fore

The project has sparked a legal and legislative battle lasting more than two years over landowners' rights and the right of expropriation, a legal maneuver that allows a company to take property for projects in the public interest.

“Many candidates have said South Dakota is open for business but not for sale, and that was proven last night,” Odenbach said.

Mortenson and some other Republican leaders a law passed during the last legislative session to maintain a regulatory path for the pipeline while ensuring that landowners received additional protections. This put them at odds with some in their own party who called for stronger measures, such as a ban on carbon pipeline expropriation. Some members of that caucus are collecting signatures on a petition to put the bill passed in the last session to a public vote in November.

Odenbach said the pipeline debate is not over yet.

“We will come back next session to further define public use and who may use the right of expropriation in South Dakota, as I attempted to do during the last session,” he said.

Incumbent Rep. Aaron Aylward (R-Harrisburg) won his primary. He is chairman of the South Dakota Freedom Caucus, which has clashed with Republican leadership. On the subject of pipelines, he said: “Things are not looking good for carbon pipelines, that’s for sure.”

Aylward said incumbents lost on Tuesday because “people are fed up with the same bureaucratic garbage they've been fed for years.”

In the Black Hills, meanwhile, rising property taxes have energized many Republican voters. Former Rep. Tim Goodwin of Rapid City won one of the two Republican nominations for the House of Representatives in the 30th District on Tuesday. He and incumbent Rep. Trish Ladner of Hot Springs will face a Democrat in a race for two House seats in November.

“Out here, property rights aren't even on the radar,” Goodwin said. “It's about property taxes.”

Lubricating the open primary wheel

Some Republicans see the intra-party friction as self-defeating. Pat Powers, author of the Dakota War College political blog, said Tuesday's primary results offer Democrats a chance to win some general elections if they position themselves in the middle of the political spectrum. Currently, Democrats hold only 11 of the 105 seats in the House.

“It could well mark a turning point in the fortunes of the Republican Party,” Powers said.

Powers said Republicans' internal infighting also means an open primary has a better chance in the November general election. The primary would change some primaries to allow all candidates for office to participate, rather than splitting candidates into party-specific primaries.

Tuesday's low voter turnout and the weak performance of incumbents gave ammunition to supporters of open primaries, Powers said.

“They can say, 'Look what happens when we don't have open primaries,' and they have the money to spread that message.”