In Colorado and South Carolina, the GOP's embattled front-runner had another very bad day. Donald Trump’s struggle to win loyal delegates to the Republican National Convention grew even more desperate on Saturday, with crushing losses in Colorado and South Carolina that put victory at a contested convention further from his grasp. Trump, who handed the reins of much of his campaign this week to strategist Paul Manafort in an effort to shore up his operation before the nomination slips away, was swept out of delegate slots up for grabs at Colorado’s state convention. Adding to his woes, he picked up...