Zeman leads polls and should pick up a strong vote outside Prague and other cities on Friday and Saturday, but is expected to fall short of winning over 50 percent of the vote and may face a strong challenger in a run-off set for January 26-27.
One of Milos Zeman's first acts as president was highly symbolic.
After casting his ballot in Prague on Saturday, Lubos Seidl told AFP that for him the election boils down to "a clash between the people who think the old way and those who think the new way".
That reassurance did not last long. He adds that "today the Czech Republic is divided as never before by President Zeman and where he places his loyalties".
After voting in Prague on Friday, Drahos said the future president "should work in the interest of the pro-Western orientation of the Czech Republic" in a clear dig at Zeman. That's true about Jiri Drahos, Michal Horacek and Pavel Fischer.
Another presidential candidate, former prime minister Mirek Topolanek, said Babis's support for Zeman is related to the fact that Zeman announced on Wednesday that he would want Babis to present signatures of a majority of MPs supporting his next government before he would appoint him prime minister again.
Among his closest advisers is the founder of the Czech subsidiary of the Russian oil giant Lukoil.
The president also made improving relations with Beijing a priority, hosting the Chinese president in a lavish state visit.
"Not everyone has seen these relationships beneficial to the country", says Cameron.
President Zeman's most serious challenger - the former head of the Czech Academy of Sciences, Jiri Drahos - is no less blunt.
Babis said on Thursday that he would vote for Zeman.
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"He has damaged our standing internationally, he has alienated key economic and security partners, he has cheapened the public discourse and increasingly he is indulging extremists". The woman, who Femen said was a Ukrainian citizen, was detained by security guards.
Certainly his, as he calls them, are infamous.
In 2015, for example, he warned the people of South Moravia to prepare for an invasion of Muslim migrants. Two years later, he was the keynote speaker at a conference of the anti-immigrant SPD party.
This has caused widespread surprise since Zeman, who was a communist, describes himself as a leftist.
But Prague wine bar owner Eva Simova, 53, told AFP that she was voting for Drahos: "He seems like an honest guy and what's more, I'm sick and exhausted of Zeman". "Sometimes he behaves like he's not our president, and I'm embarrassed".
"I like that he speaks to voters", said Irena Matuskova, a Prague nurse who plans to vote for Zeman. Suffering from type 2 diabetes and related nerve damage to his big toe, he is barely able to walk during public appearances, and leans heavily on a cane.
If the talks stretch out beyond then, Mr Babis may have a harder time with some of Mr Zeman's opponents.
"In Czech we say that "the fish stinks from the head" and this perfectly sums up Zeman's presidency", he told the BBC. "They are targeting liberal voters from the cities".
If opinion polls are correct, voters are willing to re-elect him.
But if one of his rivals can unseat him, it will represent a major departure for Czech politics as the country marks its 25th birthday.