If anyone can dance the complicated minuet required to both court Europe and not provoke Moscow, analysts and diplomats concur, Mr. Poroshenko can.

Mr. Poroshenko has proved business negotiating skills, a pragmatic streak and long experience in the fractious Ukrainian government. He was the foreign minister in 2009 and 2010 and the trade minister after that, telling Agence France-Presse last week, “I know Putin; I have had extensive experience in discussions with him; he is a strong and tough negotiator.”

But what Mr. Putin thinks of him remains unclear. On the positive side, Mr. Poroshenko has certain attributes that look good from Red Square. He has ties to Russia’s business elite, having invested heavily here. He is known to make pilgrimages to Russian Orthodox monasteries. His son met his daughter-in-law in St. Petersburg, Mr. Putin’s hometown.

Russia did not go so far as to condemn him as a Nazi sympathizer, its main taint against a raft of Kiev politicians. He is, as one analyst not authorized to speak publicly said, seen by the Kremlin as “rukopozhaty,” or someone with whom you are willing to shake hands.

Mr. Poroshenko’s main conduits to the Kremlin are believed to include Dmitry V. Firtash, a Ukrainian oligarch. Mr. Firtash helped to consolidate Mr. Poroshenko’s candidacy, but he is now stuck in Vienna, fighting extradition to the United States on corruption charges. On a certain basic level, however, none of that matters, analysts said.

“Russia does not think about individuals,” said Yevgeny Minchenko, an expert on Ukraine at the International Institute for Political Expertise. “Russia thinks about conditions, about moves, what they do. They are not worried about who you are; they only worry about what you do.”