Contest seen as latest test of president’s grip on GOP as he urges voters to reject one of the few senior Republicans who has defied him Sign up for the Breaking News US email Contest seen as latest test of president’s grip on GOP as he urges voters to reject one of the few senior Republicans who has defied him Sign up for the Breaking News US email Hello and welcome to the US politics live blog. Voters will head to the polls in primaries across six states today, with the contest in Kentucky