Since embattled Ukrainian president Petro Poroshenko is being challenged by a comedian, it was very probably meant to be a joke. His opponent TV comedy star Volodymyr Zelensky failed to turn up for a pre-election debate this weekend, so Poroshenko found himself arguing with an empty podium in front of an audience of thousands in Kiev’s Olympic stadium.

Many of those watching are likely to have been highly-amused Zelensky supporters since in the first round of the presidential election, the actor, who has zero political experience, won more than 30 percent of the vote. By contrast Poroshenko garnered just under 16 percent. Both men now face the voters in this weekend’s runoff. All the polls indicate Zelensky is going to win.

If they are right, a Zelensky triumph will be the more remarkable because he has eschewed all the normal campaigning. He has held no rallies and given few interviews. Instead he has relied almost exclusively on social media to get his message across. And by most standards that message has been vapid. He spends most of his time in mocking attacks on Poroshenko, a wealthy oligarch, whose five-year incumbency has been lackluster and tarnished with widespread corruption allegations. Of his own policies, Zelensky has said surprisingly little.

However, the remarkable point about this election is that in one respect, Zelensky has already been president. He was the star on an extremely popular 2015 TV series “Servant of the People” in which he played a history teacher, Vasyl Petrovych Holoborodko, who was elected to lead his country purely on the basis of a video in which he lambasts the mass of corrupt politicians and the venal system that they run. The footage went viral and to his amazement, the history teacher was voted in.

By himself relying on social media, Zelensky seems to be duplicating the fictional campaign. It is clever and it may well see him become Ukraine’s sixth president. But Zelensky must take great care. If he is victorious, it will be because voters are desperate for an end to the disfiguring payola that is wrecking the economy. The one undoubted difference he promises is that he is new. But this of itself is not enough.

Zelensky wrote the script for the fictional “Servant of the People” series. Now the party that supports him has the very same name. But there is a long mile between writing a biting satirical TV show and exercising real power.

Corruption is embedded in the Ukrainian economy, its politics and its bureaucracy. Deadly Russian meddling is constant. It will take a political leader of considerable strength and savvy to turn the country around. If Zelensky becomes the new occupant of the presidential Mariyinsky Palace, he will find himself up against a vast official machine whose denizens mostly see no advantage in changing their ways. These people know time is on their side. In so many elections around the world, voters have unrealistically high hopes of candidates who promise change but quickly find how difficult it is to really bring it about. Disappointment and disenchantment are likely to arise long before any major reforms can kick in.

Therefore Zelensky, the comic screenwriter, is going to find it extremely difficult to script a happy ending for the real presidential show in which he may be about to star.