Jimmy Morales, 46, who is new to politics and campaigned under the slogan "not corrupt, not a thief," has promised a transparent government if he wins the presidency in a second round vote on Oct. 25.
It remains unclear if he will face a former first lady or conservative businessman, who are still fighting for second-place finish in Sunday's vote.
Electoral tribunal judge Julio Solorzano said it was the first time the country had experienced a tie for the No. 2 spot in a runoff. He also said the turnout was the highest seen so far in a democratic election in Guatemala, 70 percent, slightly higher than the turnout for 2011.
After the scandal that forced former President Otto Perez Molina to resign last week, analysts say Morales could hold a big advantage over either opponent in the runoff, however. As an outsider he is seen as unblemished by a discredited political system.
"I believe Morales will win in the second round, irrespective of who joins him," said Gavin Strong, a Central America analyst at consultancy Control Risks.
As votes trickled in on Monday, Morales had 23.92 percent support with 97.86 percent of polling stations counted. That was far short of the 50 percent needed for an outright victory, but he was still comfortably ahead of his rivals.
Sandra Torres, the ex-wife of former President Alvaro Colom, had 19.62 percent of the votes, just ahead of conservative businessman Manuel Baldizon.
Alejandro Maldonado, a 79-year-old conservative who became vice president in May, will serve out the rest of Perez Molina's term, handing over power on Jan. 14, 2016.
"This is the political collapse of Manuel Baldizon that no one could have imagined," said Daniel Haering, professor at the University of Francisco Marroquin. "From now on, Guatemalan politicians are going to have to respond to various political demands of the people."
Luis Fernando Mack, a professor at the Latin American Faculty of Social Sciences in Guatemala, said the electoral tribunal has a delicate situation on its hands and important decisions to make to resolve the fight for second place.
"The fight will be fierce, they're going to fight for every vote," Mack said.
Al Jazeera and wires services
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