WASHINGTON - Rudy Giuliani, John McCain (news, bio, voting record) and Mitt Romney dominate the 10-man field for the Republican presidential nomination, with Fred Thompson threatening to roil an unsettled race. Rare circumstances serve as the backdrop. The sitting Republican president and party standard-bearer, George W. Bush, has abysmal job-performance ratings. Vice President Dick Cheney doesn't want the job and there's no natural heir, a significant departure for a party that historically has nominated the next in line. The result is one of the most fluid GOP races in half a century. Giuliani, a former New York mayor; McCain, an...