Some key races

Iowa’s 1st district: Four Democrats make up a potentially strong slate of challengers to Rep. Rod Blum. Michigan’s 8th district: Rep. Mike Bishop has drawn a Democratic field that includes a former assistant Defense secretary and intelligence officer.

Kentucky’s 6th district: Rep. Andy Barr faces a Democratic field that includes the mayor of Lexington, a sitting state senator and a retired U.S. Marine lieutenant colonel. New Jersey’s 11th district: The Democratic slate includes a former federal prosecutor, Navy helicopter pilot and mother of four.