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* Leaders divided by rivalries, different programmes
* Jailed Tymoshenko hard act to follow
* Klitschko emerges as strong contender for presidency
By Richard Balmforth and Thomas Grove
KIEV, Dec 3 (Reuters) - Urbane liberals are joining black-booted skinheads to protest on the streets of Kiev, but if the Orange Revolution of nine years ago is to be repeated, they need a leader to unite them.
Enter Vitaly Klitschko, a towering world boxing champion with a doctorate in sports science, who is looking increasingly like the opposition's most powerful contender.
Protesters and commentators saw Klitschko emerging on Tuesday as a leader-in-waiting, as the opposition digs in to unseat President Viktor Yanukovich after he ditched a trade pact with the European Union to revive economic ties with former Soviet master Moscow.
"I'd stand behind Klitschko," said Grigory Parkhomenko, a 54-year-old retired factory worker at Kiev's 'opposition-occupied' city hall.
"He's earned his fortune with his hands, so he doesn't need to steal from the people."
Klitschko, the 2-metre (6-foot 7-inch) tall World Boxing Council heavyweight champion known as "Dr Ironfist" because of his erudition, is sharing the stage with a bespectacled lawyer who frets about his poor public image and a surgeon who leads a combustible far-right nationalist group in an unlikely "troika" mounting a street challenge to Yanukovich's leadership.
The outpouring of anger at Yanukovich's rejection last month of a landmark accord to deepen ties with the European Union echoes public anger at his fraudulent election victory in 2004, when mass protests overturned the result and, with it, Ukraine's post-Soviet order.
The leader then was Yulia Tymoshenko, whose electric personality and fiery speeches kept tens of thousands out in the streets through the bitterly cold winter of 2004-5.
With Tymoshenko in jail, the disparate opposition alliance faces a challenge in maintaining momentum, and unity.
For successive weekends, calls by Klitschko, former economy minister Arseny Yatsenyuk and Oleh Tyahnybok, the leader of the nationalist Svoboda (Freedom) party, have brought out tens of thousands on to the streets over Yanukovich's policy U-turn away from the West back towards Russia.
Tymoshenko's supporters would naturally gravitate to her successor as party leader, Yatsenyuk, but may find common cause and ideology with Klitschko too. They are unlikely to see much hope in the hard-line nationalists.
Klitschko benefits from a perception he is uncorrupted, not a product of the discredited Ukrainian political system but a national hero who lived abroad and made a fortune winning titles with his pile-driving punch.
In sport, he and younger brother Vladimir have towered over boxing for years. Despite being 42, he still holds one of the four world heavyweight crowns, while Vladimir holds the other three. Vitaly last defended his crown last year, defeating a German challenger in a fight stopped after four rounds.
Despite an awkward public style, Klitschko exudes a quiet strength that plays well in Ukraine. He is emerging increasingly as the field commander of the protests and could be a common candidate to take on Yanukovich.
That might not sit well though with Yatsenyuk, 39, the most tested politician of the three, who took over leading Tymoshenko's party in parliament and has led pressure for her release for months.
"Yatsenyuk is getting very nervous about the competition from Klitschko. He feels he is tugging the blanket to himself," said independent analyst Volodymyr Fesenko.
"But the authority of Klitschko is growing. He has emerged as a street leader. He led the crowd and people followed him. It is the emergence of charisma - it is not everybody the crowds will follow," he said.
Yatsenyuk and Klitschko's liberal agendas starkly differ from the Ukrainian nationalism of Tyahnybok's Svoboda, with its heavy anti-Russian overtones. Svoboda is seen by many Ukrainians as anti-semitic and homphobic, which Tyahnybok denies.
People on Kiev's Independence Square last Sunday reacted with unease when Svoboda supporters hoisted their standard - blue bearing a yellow three-fingered hand - onto the peak of the festive New Year tree alongside the national flag.
Equally, the nationalists, many of them students from the Ukrainian-speaking west and raised on a diet of Ukrainian patriotism and anti-Soviet feeling, have little regard for, say, Yatsenyuk, a man who struggles with his personal image of an aloof intellectual.
Asked a year ago by the Kyiv Post newspaper why he felt he had that image, he replied dryly: "Because I'm bald and wear glasses."
The reality is, though, that both Yatsenyuk and Klitschko rely heavily on support from the shock troops that Svoboda's superior organisation can put onto the squares of the country.
"There is hidden tension. There are contradictions and these contradictions are growing stronger ... there are sharp and tough arguments going on inside the 'troika', said Fesenko.
UNITED BY GOAL
"When a dog protects a house, it has to be mean," said Sergei Ishcenko, a 53-year-old nationalist protester. "That's what we nationalists are. We are the ones who are protecting our own land and our own people," he said.
The protesters, for now, play down their differences.
"The nationalists can seem quite radical, or they may regard us as too moderate, but what is important is that we are all fighting for one Ukraine right now and we are fighting to free it from the current powers," said Marina Ivanyuk, 18, a student of foreign relations at Kiev State University. "After that we can sort out our differences."
The Yanukovich camp appear to have sensed that Klitschko is the main threat and have moved to try to neutralise him, challenging his right to run for the presidency because of the years he has spent living in Germany away from Ukraine.
"Any serious split in their ranks will be a defeat for what is going on in the streets," said Fesenko, the analyst. "The issue of their unity is an issue of survival for the opposition." (Additional reporting by Pavel Polityuk; Writing By Richard Balmforth and Matt Robinson; Editing by Peter Graff)