KIEV, Ukraine — Ukrainians awoke on April Fools’ Day to the reality of a comedian on the verge of taking over as commander in chief.

The first-round victory for Volodymyr Zelensky, a 41-year-old entertainer who plays the president in a popular sitcom, served as a sharp rebuke by about 5 million voters of their entrenched political class. But just three weeks before a runoff election that could see Zelensky ascend to the presidency of one of Europe’s largest and most geopolitically pivotal countries, it’s far from clear what kind of change his supporters are actually voting for.

Zelensky has been so short on policy specifics that some commentators have said his campaign is pursuing a “mirror strategy”: Every voter sees in it what he or she wants. Rather than make detailed promises, he has pitched himself as an upstanding pragmatist who can take on corruption and end the war with Russian-backed separatists in eastern Ukraine. Analysts warn that Zelensky’s idealized image could quickly collide with the realities of Ukraine’s murky political system. 

After the March 31 first round of votes, Ukraine's current president, Petro Poroshenko, heads to a runoff election against comedian Volodymyr Zelenski April 21. (Reuters)

“He can’t imagine how hard this system is to break,” said Ukrainian political analyst Volodymyr Fesenko. “He probably thinks like a film director . . . and real life is much more complicated.” 

Zelensky, a political novice off screen, carried 30 percent of the vote in the first round of Ukraine’s presidential election, according to preliminary results Monday. He won more votes than the second- and third-place finishers — incumbent Petro Poroshenko and former prime minister Yulia Tymoshenko — combined. If the preliminary results hold, Zelensky will face Poroshenko in an April 21 runoff.

Tymoshenko trailed Poroshenko in the race for second place, winning 13 percent of the vote to his 16 percent. She threatened Sunday evening to challenge the results, but it was not clear Monday whether she would actually do so.

An international election monitoring mission said the Tymoshenko and Poroshenko campaigns faced allegations of nationwide vote-buying. The campaigns did not immediately comment.

“Fundamental freedoms were generally respected, and candidates could campaign freely, but numerous indications of vote-buying and the misuse of state resources undermined the credibility of the process,” the election monitoring mission, which included officials from the Organization for Security and Cooperation in Europe and the Council of Europe, said in a statement. 

Analysts see Zelensky as a strong favorite in a matchup against Poroshenko, a chocolate magnate running for a second five-year term. Voters in Ukraine’s heavily Russian-speaking southeast, for instance, seem likely to back the Russian-speaking Zelensky over Poroshenko, who has made promotion of the Ukrainian language a central plank of his platform.

Minutes after the polls closed Sunday, Poroshenko was already moving to characterize Zelensky as a risk that a country at war could not afford to take. 

“I would like to remind everyone that this is not a joke,” Poroshenko told supporters. “This is the election of the commander in chief.” 

In a merging of fact and fantasy, Zelensky’s campaign has relied largely on the image and message delivered by the character he plays in his popular TV series, “Servant of the People.” Zelensky plays Vasyl Holoborodko, a humble schoolteacher who is unexpectedly elevated to the presidency after delivering an anti-corruption tirade. 

“He’s young, progressive and is different from everything that’s come before,” said Katerina Tarasiuk, a 31-year-old real estate agent in Kiev who voted for Zelensky despite her concerns about his lack of political experience. “He’s a businessman, and he has proven himself in a lot of other areas.”

There are signs that Zelensky is beginning to form a political team. Oleksandr Danylyuk and Aivaras Abromavicius, two government ministers who resigned over what they said was Poroshenko’s lack of commitment to change, have attached themselves to Zelensky’s campaign.

The participation of those figures underscores that Zelensky is modeling his improbable rise on French President Emmanuel Macron’s surge to power more than that of President Trump. “Zelensky’s outlook is much more centrist/liberal” than other expressions of the anti-establishment wave in global politics, from Trump to Brexit, Timothy Ash, an analyst covering Ukraine for BlueBay Asset Management, said in a note to clients Monday. 

Having Danylyuk and Abromavicius “holding the economy portfolios,” Ash said, “will provide considerable reassurance to markets.” 

Zelensky has even noted that he looks a bit like Macron — the centrist, dark-horse candidate who swept to France’s presidency in 2017.

“I feel some similarity” to Macron, Zelensky told foreign journalists in Kiev last month. “And not just visually, but in terms of how we feel about the world.”

While Zelensky has focused his campaign on fighting corruption, Poroshenko has cast his candidacy as an act of resistance against Russian aggression. His campaign revolved around strengthening the military, the Ukrainian language and a Ukrainian Orthodox Church independent from Moscow. Only with him, Poroshenko argued to voters, could Ukraine continue to build closer ties to Western institutions such as the European Union and NATO. 

Poroshenko signaled Sunday that he was ready to escalate his attacks on Zelensky. He cast the comedian as a puppet of Ihor Kolomoisky, who controls the TV channel that airs Zelensky’s sitcom. Both men deny that Kolomoisky is behind the comedian’s political ambitions. 

Poroshenko also claimed that a Zelensky win would be a win for the Kremlin. 

“On April 21, we will either confirm our movement toward the E.U. and NATO or we’ll turn back,” the incumbent said.

Zelensky also favors closer ties with the E.U. and NATO but says any move to join the institutions should be put to a nationwide referendum. He has promised to negotiate with Russian President Vladi­mir Putin to end the war in the east, and he has said it is unrealistic to expect Crimea to return to Ukrainian control as long as Putin — who annexed the peninsula in 2014 — remains in power. 

Given the scale of Ukrainians’ disdain for their political establishment and their fatigue with the five-year-old war, it appears that Poroshenko faces an uphill battle in trying to discredit Zelensky. Just 9 percent of Ukrainians have confidence in their government, according to a Gallup World Poll published last month — the lowest level measured by Gallup anywhere in the world.

“The negative ads against Zelensky didn’t work — Poroshenko’s campaign needs to invent something completely different,” said Taras Berezovets, an analyst with close ties to Poroshenko’s administration. “He should move quickly, because three weeks isn’t very much.”

Troianovski reported from Moscow.