KIEV (Reuters) - As a comedian, TV host and actor, Volodymyr Zelenskiy knows how to start a show with a bang. He proved that by beating all comers in the first round of Ukraine’s presidential election.

As he plans for the grand finale, a runoff against President Petro Poroshenko on April 21, aides say he is sticking to an unorthodox campaign routine that has torn up the play book.

Appearing to turn the tables on Poroshenko, Zelenskiy on Wednesday evening accepted his challenge to take part in a policy debate. In a slick video with pumping music, he set his own conditions and gave his rival 24 hours to respond.

Poroshenko’s campaign team had hinted Zelenskiy would duck out because the comedian, who plays a fictional president in a popular TV series, would risk showing himself up.

Within 45 minutes of Zelenskiy’s video being posted on Facebook, it had been seen 141,000 times, shared more than 22,000 times and attracted 3,300 comments. It left a live countdown for Poroshenko to respond.

“You called me for a debate, dreaming that I would run away, duck out, hide. No. I’m not you in 2014,” said Zelenskiy, in a reference to Poroshenko not holding a debate during the previous election five years ago.

Poroshenko responded with a much more sober video in which he accepted Zelenskiy’s condition of holding the debate in a huge soccer stadium. But he cautioned: “Debate is not a show ... This is no time to joke around. Being a president and commander in chief is not a game.”

Zelenskiy’s response to Poroshenko offered a snapshot of how he has upstaged his more experienced rivals, winning nearly twice as many votes as Poroshenko in the first round of the election on March 31.

Shunning traditional campaign tactics such as mass rallies or erecting tents in the street to distribute leaflets, he has relied heavily on social media and comedy gigs where he pokes fun at rivals, presenting himself as an everyman who stands up to corrupt elites -- a man to whom Ukrainians can relate.

At stake is the leadership of a country on the frontline of the West’s standoff with Russia following the 2014 annexation of the Crimea peninsula and war in eastern Ukraine against Russia-backed separatists in which 13,000 people have been killed.

“NOT AFRAID TO BE CREATIVE”

Slideshow ( 8 images )

Part of Zelenskiy’s campaign team works in a large house in an upscale area of the capital, Kiev. Inside, the offices have glass walls with messages scrawled on them and are filled with volunteers in their twenties bent over laptops.

“All that we do is to not be like everyone else,” said 28-year-old Michael Fedorov, whose team manages various Facebook, YouTube and Instagram pages. “We do not want to write typical posts. We do not want to speak the words that all politicians use. We want to get away from this as much as possible.”

He said Zelenskiy had from the start opposed traditional ways of doing things. “As a result, we have one platform only – that’s the internet,” he said.

Zelenskiy invites suggestions from Facebook followers on tackling problems such as high utility bills or their choice of prime minister.

Dmytro Razumkov, Zelenskiy’s political adviser, said the comedian would not hold mass rallies before the second vote because the focus was on ensuring he comes across as authentic and transparent.

“This is a person who is not a weather vane and does not change his position depending on whether it is more comfortable for a voter or less comfortable. You have to run for president, honestly stating your position and what will you do,” he said.

One challenge is attracting voters who are not internet-savvy -- bridging the gap between online and offline.

Oleksandr Korniyenko, another senior member of Zelenskiy’s team, said one technique to get around this was emailing voters with campaign messages and encouraging them to print out the email and distribute it.

Another was encouraging Zelenskiy’s many young supporters to show his social media videos to older voters such as parents, he said.

Hoping a high turnout will favor Zelenskiy, his team is trying to ensure younger voters cast their ballots in email messages with headlines likely to make them click and read.

Slideshow ( 8 images )

“Our emails are not the typical ‘You joined such and such a political party’. Instead we might have a crazy headline,” Fedorov said.

In the first round, an email was sent out by Zelenskiy’s team with the subject line “You’ve been left out”. The message itself said “everyone has already voted except you” and urged those who had voted to encourage others to vote, Fedorov said.

“We are not afraid to be creative,” he said.

“NOT A JOKE”

Zelenskiy has 3.3 million followers on Instagram, more than French President Emmanuel Macron, German Chancellor Angela Merkel, British Prime Minister Theresa May and Italian Prime Minister Giuseppe Conte combined. Poroshenko has 234,000.

The comedian’s posts offer snapshots of his life such as working out in the gym or going for a run, and allow him to poke fun at his rivals’ expense.

When former Prime Minister Yulia Tymoshenko, who was eliminated in the first round of voting, posted a video of herself eating a hot dog at a popular gas station chain to show her common touch, Zelenskiy posted a picture of himself and his team eating a hotdog at the same chain.

“In order to not be considered as just a joke, we decided to be serious like everyone else,” he wrote underneath.

Zelenskiy is likely to come under more scrutiny over policy before the runoff, including in the debate. He is wealthy and the image of the fictional president he plays, humble and scrupulously honest, is likely to be challenged by Poroshenko.

Zelenskiy has been accused during the campaign of being the puppet of a rich businessman whose TV channel airs his shows. Zelenskiy and the oligarch deny this, and both say their relationship is purely professional.

Razumkov says the campaign has shown Zelenskiy is his own man.

“In the Zelenskiy campaign, everything is completely different. When he launched his campaign, he said: ‘I want to show how you can become president, but remain a human being.’”