A steadfast performance by Jeb Bush in Tuesday's Republican debate has halted the sense of desperation around his U.S. presidential campaign and may buy him time to counter the rise of chief rival Marco Rubio. The fourth Republican debate in the search for a 2016 presidential nominee was characterized by a steady stream of attacks against front-runner Donald Trump and mistake-free performances by Rubio of Florida and Ted Cruz of Texas, two up-and-coming U.S. senators in the race. But the most relieved candidate after the two-hour encounter inside the Milwaukee Theatre was Bush, the former Florida governor who was outclassed...