Lawyer and anti-corruption campaigner Zuzana Caputova has easily won the first round of Slovakia's presidential election.
She has just over 40% with Maros Sefcovic of the ruling Smer-SD party her nearest rival on less than 19%.
Ms Caputova came to prominence during mass protests sparked by the murder of a journalist who had been investigating political corruption.
As no candidate won more than 50%, a second-round run-off will be held.
Turnout was just under 50%.
If Ms Caputova, 45, wins the second round in a fortnight's time, she will become Slovakia's first female president.
"I see the message from voters as a strong call for change," she said early on Sunday.
A member of the small Progressive Slovakia party, which has no seats in parliament, she is a newcomer to politics, whereas her conservative 52-year-old opponent is vice-president of the European Commission.
Ms Caputova first rose to prominence when she led a battle lasting 14 years against an illegal landfill.
More recently, Slovakia has seen large anti-government rallies following the murder of journalist Jan Kuciak and his fiancée in February last year.
The protests prompted Prime Minister Robert Fico to resign.
A new suspect in the killings was charged earlier this week with ordering the murders.
Four others were charged by investigators last year.
Ms Caputova was backed in her campaign by outgoing President Andrej Kiska, who did not seek a second term in office.
The Slovak presidency is a largely ceremonial office, but the president has limited powers of veto over laws passed by parliament.