Singaporeans were set to elect a new president on August 27 if more than one candidate was found eligible to contest the polls, the prime minister''s office said Wednesday. Current president SR Nathan, 87, earlier said he would step down when his second term ends on August 31. So far, five potential candidates have indicated their interest in standing, but they have yet to meet the rigorous approval criteria, and more contenders could come forward. In a writ of election, Prime Minister Lee Hsien Loong on Wednesday announced August 17 as nomination day for the presidential election.