On Thursday, Hinson will join President Donald Trump for a rally in Sioux City, which is in Iowa's conservative northwest corner. The visit to safe territory is geared toward boosting turnout even as it ties her more tightly to an unpopular president.

Chemical fertilizers and animal waste contain nitrates and phosphorus that can get washed with rain or snowmelt into the state's rivers. That affects Iowa's more liberal urban centers which rely on rivers and lakes for drinking water.