"Our country needs unity," Poroshenko said, "and that unity today can lead to us securing a decisive win already in the first round both in the presidential election and in the mayoral election in the capital, Kiev."

Poroshenko is best known as the owner of the popular Roshen brand of chocolates. His fortune is usually estimated at about $1.3 billion. In 2000, he was a founding member of the Party of Regions, the political machine that brought ousted President Viktor Yanukovych to power. A year later, however, Poroshenko broke ranks with President Leonid Kuchma and became a leading supporter and financial backer of Viktor Yushchenko's Our Ukraine party.

He backed the Orange Revolution in 2004-05 and served in Yushchenko's government. In 2009-10, he was foreign minister. Poroshenko was named trade and economic development minister under President Yanukovych in 2012. He held the post for eight months before returning to parliament as an independent deputy from the central city of Vinnytsya. Although he is believed to have financially supported the Euromaidan protests, he did not play a leading role in the demonstrations.

Ivan Lozowy, an independent policy analyst in Kiev, says he is surprised by Poroshenko's strong showing in opinion polls. "He hasn't really been known for anything in the past several years and nothing of note has happened with him. He hasn't done anything of note in the past several months," Lozowy says. "He owns a TV channel, so he uses that sometimes as a forum. They invite him for an extended interview. Of course, they invite other politicians as well, so it is somewhat balanced. But, again, there is nothing that he's really done in the short or medium term that even sticks out a little bit." Lozowy suspects Poroshenko may have paid to boost his poll ratings, a common practice in Ukraine. He notes that a recent poll asking people whether they had heard of Poroshenko's Solidarity party revealed that almost no one had.

Perhaps the high point of Poroshenko's performance in the latest political crisis came on March 12. That night, Poroshenko visited the Crimean capital, Simferopol, in a quixotic bid to prevent the peninsula from holding a referendum on joining Russia. Widely seen amateur video showed the stoic Poroshenko walking through the dark streets of the city being hounded by hundreds of chanting, pro-Russian demonstrators:

That night in Simferopol may have elevated Poroshenko to the front ranks in the eyes of many Ukrainians, says Andreas Umland, an associate professor of political science at Kiev-Mohyla Academy. "Him being chased by these pro-Russia militiamen or Russian soldiers—that, perhaps, played a role in making him look credible and a serious politician and not just an oligarch," Umland says.

Poroshenko has been a consistent supporter of Ukraine's integration with the European Union, and he gained public sympathy when Russia embargoed his Roshen chocolates in a trade war targeted against him. When he was foreign minister, Poroshenko advocated Ukraine's NATO membership, although it is not known whether he will make that position part of his presidential campaign.