BOGOTÁ, Colombia—Ivan Duque, a 41-year-old protégé of former right-wing President Álvaro Uribe, took the most votes Sunday in the first round of presidential elections by pledging to bring order and improve a sluggish economy while strongly opposing neighboring Venezuela’s authoritarian government.
Colombians gave Mr. Duque 7.5 million votes, or 39% of the total among a field of five main candidates who offered starkly different proposals for modernizing a country that, until recently, was locked in a half-century-long guerrilla...