DALLAS, Sept 10 - One year after Charlie Kirk's assassination, the organization he co-founded, Turning Point USA, has grown dramatically, expanding its presence at colleges and high schools and cementing itself as a force in Republican politics.But some of the young voters Kirk helped bring into the party are not proving uniformly loyal to Republican President Donald Trump, testing the coalition that helped return him to the White House in 2024.Kirk will be memorialized at the Republicans' first-ever midterm convention on Thursday, exactly one year after he was killed, as the party confronts signs of slippage among young men, a...