By Jeff Mason WASHINGTON (Reuters) – Republican presidential candidate Nikki Haley on Sunday accused party leaders of not being honest brokers in her campaign against Donald Trump and said she did not have to win the nominating contest in South Carolina to stay in the race. Haley, a former U.S. ambassador to the United Nations, told NBC’s Meet the Press that the former president would become even more “unhinged” as the campaign for the Republican presidential nomination progressed. Haley is trying to gain momentum against Trump after coming in third place behind him in the Iowa caucuses and se…