Opinion polls show Poroshenko trailing behind comedian Volodymyr Zelenskiy, who plays the nation's president in a hugely popular TV series, and former Prime Minister Yulia Tymoshenko.
Election officials said Friday that a record 44 candidates have registered for the March vote — including an obscure man who has the same last name and initials as Tymoshenko. She accused Poroshenko on Friday of trying to confuse voters and erode her support with the man's inclusion on the ballot.
The nation has a long history of vote-rigging and other election fraud.
Ukraine has struggled economically following Russia's 2014 annexation of Crimea and its support for separatists in eastern Ukraine, leading to a sharp decline in living standards that has hurt Poroshenko's image. The government's failure to combat corruption has also eroded his popularity.
"We have moved past the worst," the 53-year-old Poroshenko said. "The crisis caused by the war, economic aggression and the Russian blockade is easing. The renewal of economic growth will open opportunities to restore living standards."
Poroshenko has sought to shore up his sagging support by spearheading the creation of a new Ukrainian Orthodox Church independent from Moscow Patriarchy.
Earlier this month, the newly elected head of the independent Ukrainian Orthodox Church officially assumed office in Kiev, a month after the church severed its centuries-long ties with the Russian Orthodox Church.
Metropolitan Epiphanius I, 40, was enthroned during a lavish service at St. Sophia Cathedral on Feb. 3 that was attended by both Poroshenko and Tymoshenko.