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".
Czechs concluded voting in a presidential ballot on whether to re-elect incumbent Milos Zeman, a frequent critic of European Union policies and a supporter of Russian leader Vladimir Putin, for a second five-year term.
Babis dismissed the view that he made a power pact with Zeman. First round results are due out later Saturday.
Its platform has been a fierce anti-immigration discourse and an open contempt for minorities and refugees.
While he has won support among many Czechs by criticizing intellectual elites, they say he's sown doubt over whether the country of 10.6 million people should remain in the world's largest trading bloc.
In 2015, for example, he warned the people of South Moravia to prepare for an invasion of Muslim migrants. "The beauty of our women will be lost", he told the crowd, "because they'll be shrouded in burkas".
"Although I can think of certain women for whom that would be an improvement", he added.
Among the leading candidates, Zeman has been the most outspoken on migration, linking Muslim immigration to security threats.
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.
British Prime Minister wants to cut all avoidable plastic within 25 years
The overall plan was "a cynical attempt at rebranding the Tories' image and appears to contain only weak proposals", she said. However, opposition leaders and environmental campaigners were quick to condemn the proposals as dangerously insufficient.
The Czech presidency is largely ceremonial but has an important role in picking who should form a government.
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.
One of Milos Zeman's first acts as president was highly symbolic.
Among his closest advisers is the founder of the Czech subsidiary of the Russian oil giant Lukoil. "Data also show a deepening rift between cities and the countryside". Today the country is split like never before over President Zeman and where his true loyalties lie.
"Prague Castle needs to be fumigated", Michal Horacek, music producer, betting agency entrepreneur and now candidate for president, told the. Jiri Drahos - a 68-year-old chemistry professor and former chief of the academy of science - is the most likely candidate to advance.
This has caused widespread surprise since Zeman, who was a communist, describes himself as a leftist.
First-time voter Klara - who turns 18 on the second day of polling - would like to see a change of direction.
"I think President Zeman does not represent the country as he should", he told the BBC, "sometimes he behaves as if he were not our president, I'm ashamed". 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.
The act went some way to reassuring at least some of the urban, liberal, pro-European Czechs - most of whom did not vote for him - that the country's geopolitical position would, perhaps, be secure in his hands after all.