Caputova, who was the front runner having won the first round more than 20 percentage points ahead of Sefcovic, campaigned to end what she calls the capture of the state «by people pulling strings from behind», a message that opinion polls show resonates with younger, educated voters.
The 45-year old member of a liberal non-parliamentary Progressive Slovakia party has been endorsed by opposition parties and a junior party in the ruling coalition that represents the ethnic Hungarian minority, as well as outgoing President Andrej Kiska.
«I don’t take my victory as a given. I expect a narrower result than two weeks ago,» Caputova said after casting her vote in her hometown of Pezinok.
Sefcovic, who voted in Bratislava, said he hoped for a high turnout that would give the new president a strong mandate.
«Slovakia needs reconciliation and peace because divisions in the society take away our energy from important issues,» he said.
Polling stations closed at 10 pm with results expected overnight.
At one polling station in the capital, voter Zuzana Behrikova said she had been convinced by Caputova’s activist background.
«She knows what it is like to face injustice and she has always had the back of those who fought against the oligarchs,» Behrikova said, accompanied by her two young daughters.
Slovakia’s president wields little day-to-day power but appoints prime ministers and can veto appointments of senior prosecutors and judges.
Five people have been charged with the murders of Kuciak and his fiancée Martina Kusnirova, including businessman Marian Kocner, who was investigated by Kuciak, and who has become a symbol of perceived impunity after more than a decade of rule by Smer. Kocner denies any wrongdoing.
The killings ignited the biggest protests in Slovakia’s post-communist history.
Caputova waged a 14-year fight with a company Kocner represented that wanted to build an illegal landfill in her home town. She eventually won the case, earning her the nickname «Slovakia’s Erin Brockovich», after the American environmentalist portrayed by Julia Roberts in a 2000 film.
An opinion poll by the Focus agency, carried out the day before the vote, put support for Caputova at 55.2 per cent. Sefcovic, who has campaigned on his experience and personal relationships with foreign leaders, held a 44.8 per cent vote share, according to the poll.
Courting voters who backed anti-immigration candidates in the first round of the presidential election, Sefcovic has said he rejects the vision of an EU «where the distribution of migrants would be decided by someone other than Slovakia».
The Moscow-educated politician supported the government’s opposition to mandatory migrant quotas suggested by the European Commission, where he is a vice-president.
Sefcovic, who joined the Communist Party in what was then Czechoslovakia just months before communism collapsed in November 1989, has stressed his Christian beliefs in the campaign. He called Caputova’s support for abortion rights and LGBT rights «ultra-liberal».