By Helen Murphy and Julia Symmes Cobb BOGOTA (Reuters) – Colombians vote on Sunday in a tightly fought presidential election that has seen the top two candidates tainted by scandal as they wrestle over the pivotal issue of how to end a five-decade insurgency by Marxist FARC rebels. The battle for the presidential palace in Latin America’s No. 4 economy is between incumbent leader Juan Manuel Santos and bitter rival Oscar Ivan Zuluaga, a right-wing economist whose late surge in polls has left them neck-and-neck. Though once cabinet colleagues as the ministers of defense and finance respectively, Santos and Zuluaga differ sharply on how to end a conflict that has killed more than 200,000 people and gave Colombia a basket-case image it shed only in recent years. “We are deciding between war and peace and you can’t make peace overnight,” said Jhon Jairo Ramirez, a 29-year-old Bogota shoe-shiner who remained undecided on which way to vote.