WICHITA, Kan. (AP) — Eleven biofuel plants dot the rural expanse of western and central Kansas, so farmers and residents there were surprised when their Republican congressman called for ending a federal program that supports demand for biofuels. Their anger has now come back to haunt Rep. Tim Huelskamp.

Huelskamp, a tea party favorite, is locked in a tough primary race with a GOP opponent, Alan LaPolice, who supports the renewable energy standards. The primary election is Tuesday.

A political action committee supported by farmers is spending more than $260,400 to oppose Huelskamp. And a group of Kansas agricultural groups issued a scathing statement criticizing him.

Huelskamp maintains that the federal program, which mandates the use of biofuels in gasoline, interferes with the free market. The measure he co-sponsored is pending in Congress.