Exit polls and partial results in Uruguay say the candidate of President Jose Mujica’s party has won most votes in the presidential election.
But Tabare Vazquez appears to have fallen short of the outright majority needed to avoid a run-off next month.
If confirmed, Mr Vazquez of the Broad Front party will face Luis Lacalle Pou of the right-wing National Party.
President Mujica is barred by the constitution from running for a second consecutive term.
Three separate exit polls showed Mr Vazquez winning with 44-46% of votes and Mr Lacalle Pou trailing behind with 31-34%.
Partial official results also appeared to confirm that the election will go to a second round on 30 November, as no candidate obtained at least 50.1% of the vote on Sunday.
Tabare Vazquez served as president of Uruguay in 2005-2010 and remains one of the most popular politicians in Latin America.
BBC correspondent Ignacio de los Reyes says the presidential run-off is expected to be tight as Mr Vazquez’s young contender, Luis Lacalle Pou, who is the son of a former president, became a rising political star in recent months.
They have both promised to keep social spending high and boost the economy.
Mr Mujica remains popular after leading Uruguay through economy growth and wage rises, but he is barred by the constitution from running for a second consecutive term.
His government was behind social reforms such as the legalisation of marijuana, abortion and gay marriage.
But critics say it has failed to deal with problems in education, security and environmental protection.
Uruguayans were casting ballots for president, vice-president and members of parliament at the same time. The Broad Front could lose its current majority in Congress.
They were also voting in a controversial referendum on whether to lower the age at which a person can be criminally charged as an adult from 18 to 16.