Six US states hold primaries as Trump urges Kentucky voters to oust Massie

Republican critic of president faces challenge from Ed Gallrein, while Georgia and Pennsylvania hold key contests

The biggest day of primaries yet arrives Tuesday, with voters in Kentucky, Pennsylvania, Georgia, Alabama, Oregon and Idaho, heading to the polls to select candidates ahead of November's midterm elections.

While many primaries will be resolved with little drama, some have shaped up to be among the most contentious elections of the year so far, serving as gauges of Donald Trump's control of Republicans, and the direction Democratic voters are looking to steer their party as they seek to retake control of Congress.