Opposition-backed candidate Park Won-soon appeared headed for a resounding victory in Wednesday\'s by-election for Seoul mayor, which is seen as a significant test of voter sentiment ahead of next year\'s parliamentary and presidential votes. With 31.3 percent of the votes counted, lawyer-turned-activist Park was leading with 53.3 percent against his ruling Grand National Party rival Na Kyung-won\'s 46.3 percent, according to the National Election Commission (NEC).