A bitterly contested Republican congressional race unfolding in south-central Kansas is testing the political influence of big corporate money in the backyard of two billionaire brothers who have poured millions into races across the nation.

The 4th District GOP primary Aug. 5 pits U.S. Rep. Mike Pompeo of Wichita against the popular conservative Republican who previously held that position. Former congressman Todd Tiahrt, also from Wichita, gave up the House seat in 2010 in an unsuccessful primary run for the U.S. Senate.

Tiahrt’s primary challenge comes in the home district of Charles and David Koch, who have sent much of their personal fortunes to a network of conservative organizations nationwide. Koch Industries’ employee political action committee, KochPAC, supports Pompeo and has given him the maximum allowable