An extraordinary row has broken out in the United States between Donald Trump and leaders of the Republican Party that he's battling to representing this November's Presidential election. Mr. Trump says that Republican grandees are using "dirty tricks" in a bid to stop him from becoming the Party's candidate. The Party has hit back, with its chairman accusing Mr. Trump of failing to understand the process by which party supporters choose a winner. So what is going on in the US election campaign? Simon's report aired on stations worldwide. #Trump #GOP #Election #Obama #WhiteHouse