By Prak Chan Thul PHNOM PENH (Reuters) -Polls opened in a one-sided election in Cambodia on Sunday that is certain to prolong the ruling party's dominance of politics, clearing the path for a historic leadership transition and the end of the reign of one of the world's longest-serving premiers. The contest is effectively a one-horse race, with Prime Minister Hun Sen's Cambodian People's Party (CPP), a political behemoth with a vast war chest, facing no viable opponent after a ruthless, years-long crackdown on its rivals. Former Khmer Rouge guerrilla Hun Sen, 70, has led Cambodia for 38 years a...
