Around 4.4 million Slovakian voters will elect a new president in a run-off election on Saturday.
Polls indicate a neck-and-neck race between the social democratic parliamentary speaker Peter Pellegrini and the liberal former foreign minister and diplomat Ivan Korčok.
The liberal incumbent Zuzana Čaputová is not running for a second five-year term despite her continued popularity.
The office of president has more of a representative function in Slovakia, which is a member of both the EU and NATO.
The election is overshadowed by the war in neighbouring Ukraine, while Slovakia is deeply divided over domestic issues.
Its three-party government made up of two social democratic parties and a right-wing populist/Pro-Russian party is at loggerheads with the liberal and conservative opposition about the war in Ukraine, but also about the rule of law and democracy.
Korčok, who was supported by the opposition parties, surprisingly won the first round of voting on March 23 with a 5.5 percentage point lead over Pellegrini.
A decisive factor will now be how the supporters of the eliminated candidates behave. The result of voting is expected early on Sunday.