The states holding elections Tuesday include some of the toughest terrain Democrats are defending this year.
Primaries are on tap in Kansas, Michigan, Missouri, and Washington state, and they include contests that will determine whether core voters agree with party leaders on who has the best chance in swing seats.
Michigan’s primaries will set the lineups for a toss-up Senate contest and for two open-seat House races where the district lines drawn by an independent commission give both parties a clear shot. All of those races will be key to determining who controls Congress.