Liberal environmentalists and conservative landowners, led by the former congressman Steve King, are pressuring Republican candidates to oppose three Midwestern pipelines.
Climate change provisions in the Inflation Reduction Act have spurred developers to build ambitious renewable energy projects that turn corn into ethanol and manure into methane.
Plans that would bury carbon underground rather than release it in the air have stoked debate over climate and property rights, creating unlikely alliances and stirring memories of fierce battles over oil.