US President Donald Trump tightened his grip on the Republican Party on Tuesday as Kentucky voters ousted one of the few conservative lawmakers willing to challenge him openly.Congressman Thomas Massie’s defeat, which he conceded some three hours after polls closed, marked another victory in Trump’s campaign to punish Republican dissent.It follows the rout of Indiana state lawmakers who defied the US president on redistricting and the weekend collapse of Senator Bill Cassidy’s re-election bid in Louisiana.Massie’s loss came after months of attacks from Trump, more than US$32 million in ad spending and an unusual campaign appearance by Defence Secretary Pete Hegseth on behalf of Trump-backed challenger Ed Gallrein, turning a once-sleepy Kentucky primary into a national loyalty test.Several states held primaries Tuesday to pick candidates for the November midterm elections, but the standout contest was in Kentucky. Massie, a seven-term congressman, has been one of the president’s most persistent internal critics.The race was being watched as a measure of whether Trump’s grip on Republican voters remains strong despite war, inflation and sliding national approval ratings – and whether there is still room in the party for lawmakers willing to break with him.