But he faces a seasoned and ruthless campaigner in Zeman, who received only 24 percent of the vote in the first round of the 2013 election - the first time a Czech president was elected by direct vote - but more than doubled his share in the second round after running what was widely branded a smear campaign against his opponent.
Zeman's inclination towards far-right groups and his warm relations with Russian Federation and China have split public opinion, with a sizeable chunk of the electorate favouring pro-western candidates, including 68-year-old academic Drahos.
While the Czech Republic is the EU's richest post-communist member by economic output per capita - it also has the bloc's lowest unemployment and one of its fastest growth rates - Zeman has tapped into anti-migrant rhetoric resembling that of anti-establishment forces that scored gains in European elections a year ago. First indications were that Zeman, who according to pre-election polls was expected to win 43-44% of votes cast nationwide, performed worse in rural areas of Czechia than was anticipated.
Drahos, 68, is seen as more western-oriented.
He has also lashed out against the EU's efforts to integrate refugees from the Middle East and Africa, once saying that Muslim migrants will impose Sharia Law, chop off thieves' hands and stone adulterous women in Europe.
Security personnel also had to help a visibly rattled Zeman, who walks with a cane, to leave the room. He has criticised migration from Muslim-majority countries as well as Germany's decision to accept many migrants. "It's clear that not everyone can agree, but the current president doesn't unite people, he divides them", Drahos added.
Jiri Drahos addresses the media after the announcement of the preliminary results of the presidential elections
Most of the early results came from rural areas where Mr Zeman's support is high.
"The polarisation of society has deepened in the past months", Saradin said.
"It is a clash between. the post-communist part of society represented by Zeman and the other part, say, modern, pro-Western, which simply doesn't want this president any more", he told AFP. Former diplomat Pavel Fischer was third with 8.8 percent. The outcome may also influence Czech Prime Minister Andrej Babis's chances of forming a cabinet.
Babis's populist ANO movement won last October's general elections with its anti-corruption and anti-euro campaign, but the Slovak-born tycoon facing police charges over European Union funding fraud failed to woo coalition partners.
The Czech government is led by the prime minister, but unlike other countries where the president has a largely ceremonial role, the Czech president is involved in numerous country's political decisions. Babis said Thursday he'd vote for Zeman in the election.
But things could change dramatically if Drahos wins. "I'm still young, full of strength and full of energy and I look forward to debate", he remarked, while urging supporters to bring along their close ones, including "relatives and lovers", to the second-round polling stations.
Soon after that initial results will indicate which two candidates are likely to contest the expected run-off vote.