KIEV, Ukraine — In early January, a tall man in a gray coat walked through the crowds in Kiev's Independence Square. The atmosphere was electric. Three months of protests had resulted in deadly clashes between demonstrators and security forces. From Washington to Moscow, the world was waiting to see what would happen next.
A few in the crowd recognized the man. "Klitschko!" they shouted. "That's Klitschko!"
Ukrainian opposition leader Vitali Klitschko, the 6-foot-7 former world heavyweight boxing champion, responded with characteristic humor.
"No, I'm his brother," he said before climbing onto a stage to address 10,000 people.
Mr. Klitschko's younger brother, Wladimir, is the current world heavyweight boxing champion. Until recently, he was the sibling most likely to command vast audiences.
Lately, however, the attention has been squarely on the elder Mr. Klitschko, who is a serious contender to lead this Slavic country of nearly 45 million people.
Vitali Klitschko, 42, heads the Ukrainian Democratic Alliance for Reform, one of three opposition parties that came to power last month after street protests ousted President Viktor Yanukovych. The party's acronym, UDAR, spells out "strike," or "hit," in Ukrainian.
Mr. Klitschko didn't take a seat in the government he helped create. Instead, he announced soon after Mr. Yanukovych fled Kiev that he would run for president in the newly scheduled May 25 elections.
"The main fight of my life is going on today," Mr. Klitschko told The Washington Times. "In politics, I've seen a lot — games without rules, dirty tricks, cunning. But I'm not used to giving up. I stayed in politics for the sake of my principles, for the goal that I had, and I was rewarded.
"I've seen Maidan [Independence Square]. I witnessed the courage and fortitude, braveness and self-sacrifice. This winter, I stood near real heroes — the people who wrote the new history of Ukraine under bullets.
"Our task today is to save Ukraine, save peace and sovereignty, unity and integrity, to build a new country," he said. "I have no right to let these people down."
Humble but cagey
His presidential announcement set the stage for a confrontation between Mr. Klitschko and the colossus of Ukrainian politics — the blond-braided Yulia Tymoshenko, the former prime minister and Orange Revolution leader who was imprisoned in 2011 on a widely disputed abuse-of-power conviction. Parliament freed her late last month after the Yanukovych regime collapsed.
Mr. Klitschko entered politics eight years ago and won a seat on Kiev's City Council. He ran twice for mayor unsuccessfully.
But he also organized UDAR, which two years ago won 14 percent of the vote, enough to become the third-largest party in parliament.
UDAR lawmaker Pavlo Rozenko said Mr. Klitschko is a sincere politician, a rare find in Ukrainian politics. He recalled how Mr. Klitschko reached out to him in the summer of 2012 as he was expanding the party.
"The meeting wasn't scheduled in advance, and I was outside Kiev. But Klitschko just said, 'OK, I'll come to you,' and made a drive. I was pleasantly impressed about how it was OK for the party leader to just jump in a car and come meet a potential member," said Mr. Rozenko.
The former heavyweight champion is also humble, the lawmaker said.
"He is never ashamed to admit that he doesn't know something and to ask about it," said Mr. Rozenko. "He is always willing to learn."
But Mr. Klitschko also is a tactician who continually sizes up opponents and friends.
"I think it is a psychological skill he brought from his career in boxing," Mr. Rozenko said. "It helps him choosing right people for his team."
Critics say Mr. Klitschko was too quick to seek an agreement with Mr. Yanukovych after the bloodshed in Kiev, a move that could cost him support with the protesters in Independence Square.
'New faces, new decisions'
Even so, Mr. Klitschko's role as a moderate voice in a country where politicians often exploit cultural tensions has given UDAR broad appeal.
"He can unify Ukrainians to some extent because he knows the Russian-speaking Ukrainians. He made a statement on Independence Square, and he was speaking in Russian, directing his message to Russian-speaking Ukrainians," said Serhiy Solodky, deputy director of the Institute of World Policy in Kiev. "Lots of people from different regions of Ukraine voted for him in the last parliamentary elections. We can talk about him as a unifying candidate."
That style has given him good standing among Ukrainians who are weary of Ms. Tymoshenko and other longtime politicians.
"Ukrainians are tired of the old faces in politics," said Mr. Solodky. "Ukrainians need new faces, new decisions, new ideas. They need a kind of dream politician, and Klitschko was a reflection of this dream. He was a reflection of a success story for Ukrainian citizens. That is why lots of people respected him, trusted him, and want to see him as a president."
Protester Olena Dubovik, a Kiev student, agreed.
"I don't have much admiration for any political leaders, but I think I would vote for Klitschko at presidential elections," said Ms. Dubovik. "I like that he got rich in a clear legal way, not through some murky schemes like some other top politicians here."
Still, Mr. Klitschko's raw, straightforward manner sometimes backfires on him.
When he was trying to calm a crowd during a January street protest, he was caught cursing at demonstrators who scuffled with him. He also has been videotaped cursing at reporters who intently challenge and question him.
Even Mr. Klitschko acknowledges he is not polished.
"When I started my political career, public speeches were tough for me," he told a radio interviewer late last year. "The key thing is to speak from your heart."
Despite the outbursts, Mr. Klitschko last month was among a group of Ukrainian opposition figures chosen to journey to Berlin with new Prime Minister Arseniy Yatsenyuk to ask German Chancellor Angela Merkel for aid from the European Union. He apparently impressed delegates on the mission.
"Victory for Ukraine means a modern European state with stable institutions," he said, delivering comments in articulate German during a press conference. "It is in the interests of the European Union that Ukraine is political and economically stable because instability in Ukraine can lead to instability in the whole region."
• Luigi Serenelli in Berlin contributed to this report.