Opinion surveys show the divisive 73-year-old ex- communist, who is also staunchly anti-Muslim and pro-Chinese, leading the pack of nine candidates ahead of Jiri Drahos, 68- year-old pro-European former head of the Czech Academy of Sciences.
Although Zeman is in pole position as the country kicks off a final day of first-round voting today, the outspoken head of state is unlikely to win an outright majority. A run- off vote is expected on January 26-27.
Zeman was targeted by a bare-breasted anti-Kremlin protester who called him "Putin's slut" as he voted in Prague yesterday, a move experts said might boost his chances judging by an outpouring of sympathy for him on social media.
The topless protester from Ukraine's Femen group was overpowered by bodyguards and then arrested by police.
Security personnel also had to help a visibly rattled Zeman, who walks with a cane, to leave the room.
But Prague wine bar owner Eva Simova, 53, told AFP that he was voting for Drahos: "He seems like an honest guy and what's more, I'm sick and tired of Zeman."
A recent poll for Czech Television showed Drahos winning a second round vote with 48.5 per cent support against 44 per cent for Zeman.
Zeman's rhetoric echoes populist-minded eastern EU leaders -- especially in Hungary and Poland -- at odds with Brussels over mandatory refugee quotas and various rules they see as attempts to limit national sovereignty.
He is also stridently anti-Muslim, having once called the 2015 migrant crisis "an organised invasion" of Europe and insisted Muslims were "impossible to integrate".
The country of 10.6 million people has received only 12 migrants under the EU quota system.
Drahos could not be more different. A mild-mannered liberal centrist whom critics have dubbed "wishy-washy", he has called for Prague to "play a more active role in the EU" and has backed the adoption of the euro currency.
After voting in Prague today, Drahos said that the future president "should work in the interest of the pro-Western orientation of the Czech Republic" in a clear dig at Zeman.
"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.
Zeman has the backing of embattled billionaire Prime Minister Andrej Babis, who said the incumbent "fights for our national interests" but called on him to "unite, not divide" Czechs.
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 EU funding fraud failed to woo coalition partners.
Tapped by Zeman for prime minister in December, Babis was forced to form a minority government which appears set to lose a parliamentary confidence vote on January 16.
Pehe said a victory for Zeman might "pave the way for a deeper alliance with Andrej Babis, which could lead to a change in some basic parameters of liberal democracy in the country."
But the situation could change dramatically if Drahos wins.
"Drahos has made it very clear that a prosecuted man should not be prime minister," Pehe said.
Polling stations reopen at 0700 GMT today before closing at 1300.
Soon after that initial results will indicate which two candidates are likely to contest the expected run-off vote.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)