( CNN ) -- Colombians cast ballots in a hotly contested presidential vote on Sunday , but none of the five candidates running received enough support to win the election . In the preliminary tally , Oscar Ivan Zuluaga was in the lead with 29.3 % of votes , officials said , while incumbent President Juan Manuel Santos had secured 25.6 % of votes . To win a presidential election , Colombian law requires a candidate to obtain more than 50 % of votes . That means Zuluaga and Santos will face off in a runoff election on June 15 . A key question voters are weighing : Should Colombia 's government keep negotiating with leftist guerrillas or force them to surrender ? Santos was first elected in 2010 on a platform of continuing an offensive against the Revolutionary Armed Forces of Colombia , or FARC , leftist guerrillas that have been at war with the government for decades . But since late 2012 , peace talks with the group have become a hallmark of his presidency . On Sunday , Santos said that in the second round , voters will choose `` between the end of the war and a war without end . '' `` We are going to choose between those who respect the opposition and the free press , and those who prefer intolerance , '' he said . Zuluaga has called for an end to the peace talks and is against giving any political space to the rebels . On Sunday , he stressed that he also wanted peace for Colombia . `` Peace , yes , but peace that benefits the people , '' he said . `` My pledge is to work for a serious , responsible and lasting peace . '' `` The difference regarding the candidates ' position in the economy and other issues is minimal , but when it comes to how to handle the guerrilla , it 's abysmal , '' pollster Javier Restrepo told CNN last week . `` Santos is advocating for a continuation of the peace talks he started in 2012 , while Zuluaga 's position is that there should not be a dialogue with an illegal guerrilla until its fighters surrender to government forces and lay down their weapons . '' Election observers from the Organization of American States said there was a high level of abstention in Sunday 's vote , with around 60 % of eligible voters deciding to stay home rather than cast ballots , CNN en EspaÃ±ol reported . As candidates debated the issues , a scandal involving a hacker and a video sent shockwaves through the final days of campaigning last week . The video published by the weekly news magazine `` Semana '' in BogotÃ¡ allegedly shows Zuluaga getting secret military information from a man who was arrested earlier this month and accused of illegal hacking activities . Zuluaga told reporters the five-minute video was `` a vulgar montage '' put together to smear his campaign . CNN 's Mariano Castillo and CNN en EspaÃ±ol contributed to this report .
NEW : Santos : Voters will choose `` between the end of the war and a war without end '' NEW : Zuluaga : `` My pledge is to work for a serious , responsible and lasting peace '' Colombia 's presidential vote will need a second round to pick a winner . Key question voters are weighing : How should government handle the FARC ?