Costa Rican presidential candidate Johnny Araya, from the governing party, says he is abandoning his campaign for April's run-off election.
The surprise move opens the way for his only opponent, the left-leaning historian Luis Guillermo Solis, to be elected president on 6 April.
After weighing his chances, it was only sensible to withdraw, Mr Araya said.
Neither Mr Araya nor his main rival reached the 40% of votes needed for an outright victory in the first turn.
A recent opinion poll suggested Mr Araya, with only 21% of voters likely to back him, was trailing behind Mr Solis with 64%.
"It is only prudent not to spend millions on publicity, meetings and other events. We will respect the constitutional provisions, but I will refrain from any electoral activity," he told reporters.
Despite Mr Araya's withdrawal, Costa Rican law does not allow for candidates to drop out.
So the vote must still be held on 6 April and Mr Araya's name will appear on the ballot.
But it is more than likely that Mr Solis and his Citizen's Action Party will replace Costa Rica's first female president, Laura Chinchilla.
The victory would also mark another gain for centre-left parties in Latin America.
Mr Solis ran on an anti-corruption ticket and unexpectedly beat the government's candidate, even if by a margin of less than one percentage point.
The history university professor's campaign was vocally critical of the previous two governments headed by the National Liberation Party.
Mr Solis himself is a former member of the governing party.
He served as chief of staff of the foreign ministry from 1986 to 1990 and as ambassador for Central American affairs and director of foreign policy during the presidency of Jose Maria Figueres Olsen, between 1994 and 1998.
Mr Solis left the party in 2005 after allegedly finding irregularities in the party elections.
He joined the Citizen's Action Party in 2009.
Correspondents say he is set to govern with a deeply divided Congress with representatives from nine parties, none of which has a clear majority.
If confirmed as Costa Rica's president, Mr Solis will also have to tackle growing government debt and rising unemployment.