Presidential candidates in Ukraine are banned from campaigning the day before Sunday’s highly contested vote. But Ukraine’s “quiet day” has not been all that quiet.

Turn on television channel 1+1 and you’re likely to see the poll leader Volodymyr Zelenskiy starring in his own comedy show, Kvartal 95. Later on Saturday evening, 1+1 will broadcast a biopic about Ronald Reagan, another actor-turned-politician, with his voice dubbed by Zelenskiy.

On Instagram, posts by President Petro Poroshenko show him praying for “Ukrainian unity” alongside senior members of the church and army veterans. An article on his government website explained that the group also prayed “for the wisdom of the people who tomorrow will decide the future of Ukraine”.

Facebook Twitter Pinterest Petro Poroshenko poses for selfies with Ukrainians after a mass prayer for fair elections in Kyiv. Photograph: Sergey Dolzhenko/EPA

Across the country, campaign billboards have been subtly altered in order to skirt the ban on outdoor advertising while still urging supporters to get out and vote.

Ukrainians are due to vote on Sunday in the country’s most competitive elections in years. But Ukraine has had a difficult five years since a 2014 revolution. Reforms have stalled, utility prices have increased and thousands have died in a war with Russian-backed separatists in the country’s south-east.

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Zelenskiy, who plays the president on his television show, Servant of the People, is expected to win, in a vote characterised as a rebuke of the country’s leaders. Both Poroshenko and former prime minister Yulia Tymoshenko are battling to take second place and earn a place in a likely runoff later in April.

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The close finish between the second two candidates could explain the tactics, both petty and more troubling, to eke out every last vote.

A candidate by the name of Yuri Tymoshenko has been registered for the first round, perhaps fooling some of Tymoshenko’s voters into checking the wrong box. Several campaigns have complained about vote-buying. Members of a nationalist group have been deputised as official vote monitors on Sunday, raising concerns of intimidation at the polls.

Chesno, a Ukrainian non-governmental organisation that advocates for transparent elections, also said it discovered mysterious billboards which had been stripped of the candidates’ names and faces but sought to get a final word in to voters before they went to the polls on Sunday.

“Think,” read one billboard that looks suspiciously like a Poroshenko ad. “Don’t waste another five years,” reads another in Zelenskiy’s colours. And “change” read a third, where a Tymoshenko ad had previously hung.