(Bloomberg) -- The powerful public policy and political network led by billionaire Charles Koch on Monday broke from its traditional approach of backing Republican candidates by saying it wouldn’t endorse the party’s challenger to a potentially vulnerable Democratic senator, Heidi Heitkamp of North Dakota.

“We can’t support him at this time,” Tim Phillips, president of the Americans for Prosperity, the network’s flagship political organization, said of the candidate, Republican Representative Kevin Cramer. Phillips criticized Cramer’s votes on spending bills and other legislation.

Heitkamp is one of 10 Senate Democrats who face re-election in November in states President Donald Trump won in 2016. The lack of an endorsement in a key race comes as the network is trying to put forward a more bipartisan face.

The decision declining to back Cramer was announced at a briefing Monday for more than 500 donors to the network gathered for a three-day meeting that is concluding at a luxury resort in Colorado Springs, Colorado. The network, with more than 700 donors who give at least $100,000 per year, has convened such gatherings twice annually since 2003.

To contact the reporter on this story: John McCormick in Chicago at jmccormick16@bloomberg.net

To contact the editors responsible for this story: Joe Sobczyk at jsobczyk@bloomberg.net, Justin Blum, Kevin Whitelaw

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