Jackson County is a solidly Democratic county and has remained so even as the state of Missouri has trended rightward. The last Republican presidential candidate to carry the county was Richard Nixon in 1972, the only Republican to do so since 1932.

The county's Democratic lean is due almost entirely to the presence of Kansas City. In 2008, for example, John McCain barely carried the areas of the county outside Kansas City, but Barack Obama carried Kansas City by a nearly 3-to-1 margin, enough for him to carry the county as a whole with 62 percent of the vote. Generally, Democratic strength is concentrated south of the Missouri River, with the wealthier areas north of the river being more friendly to Republicans.