Polls suggest neither Mr Samper, 43, an economist who still carries inside him four bullets from a 1989 assassination attempt, nor Mr Pastrana, 39, a former mayor of Bogota, will chalk up the 50-plus per cent to clinch election. If so, the other 16 candidates will drop out and the two will run head-to-head three weeks later.
Campaigning passed relatively peacefully, with the exception of a bomb attack by guerrillas in Medellin last weekend which killed six policemen. The killing of the Medellin cocaine cartel boss, Pablo Escobar, in December has diminished the so-called narco-violence, which devastated the last election campaign in 1989-90.
President Cesar Gaviria was elected then after the previous Liberal candidate, Luis Galan, was shot dead while campaigning. Two other candidates were also killed in that campaign, one of them in mid-flight on board a commercial airliner.
Mr Samper, a former development minister and ambassador to Spain, was hit by 11 bullets in a separate attack at Bogota airport while assisting the Liberal Party campaign in 1989.
Sunday's other candidates include the former M-19 guerrilla group leader, Antonio Navarro Wolf, who lost a leg in a grenade attack in 1985. Then there is the former secret-police chief, Miguel Maza Marquez, something of a national hero for his undaunted efforts to defeat the Medellin cartel until retiring in 1991.
With the Medellin cartel largely subdued, the new president's task will be twofold: to dismantle the more subtle Cali cartel, responsible for most of Colombia's cocaine trade, and seek peace with two big guerrilla groups, whose 10,000 men control large parts of the country.Reuse content