Towering over his fellow protest leaders, reigning world heavyweight boxing champion Vitali Klitschko has emerged as Ukraine’s most popular opposition figure and has ambitions to become its next president.

Thanks to his sports-hero status and his reputation of being a new pro-Western politician untainted by Ukraine’s frequent corruption scandals, Klitschko, 42, has surpassed jailed former Prime Minister Yulia Tymoshenko in opinion polls.

As massive anti-government protests continue to grip Ukraine, Klitschko is urging his countrymen to continue their fight to turn this ex-Soviet republic into a genuine Western democracy.

“This is not a revolution. It is a peaceful protest that demands justice,” Klitschko said Wednesday. “The people are not defending political interests. They are defending the idea of living in a civilized country.”

Klitschko was one of a few opposition politicians who tried to stop several hundred radical protesters from storming President Viktor Yanukovych’s office during a demonstration Sunday that drew hundreds of thousands to the streets of Kiev, the capital. As the boxer called for peace, the jubilant crowd chanted his name.

On Wednesday, his party was one of several opposition parties to blockade the Ukrainian parliament as part of a nationwide strike.

The demonstrations in Kiev were galvanized when Yanukovych’s government sent in riot police with truncheons to break up a small, peaceful rally in the middle of the night, injuring dozens.

“They took away people’s hope to implement reforms, to change the situation in the country,” Klitschko said. “They stole our hope.”

Now Klitschko must prove that he has as much stamina in the political arena as he does in the boxing ring. In more than 15 years as a professional boxer, Klitschko has scored 45 victories in 47 fights, 41 on them with knockouts, earning the nickname “Dr. Ironfist.” He plans to have one more bout before he retires and still spends several hours a day training.

Despite earning a doctorate in sports science, Klitschko has had to fight a stereotype of being intellectually unfit to run this economically troubled, Texas-size country of 46 million. Having been raised — like many Ukrainians — in a Russian-speaking family, Klitschko just recently learned Ukrainian and sometimes struggles to find the right word. But at the same time, he appeals to many Ukrainians, with his air of sincerity and his image of a handsome tough guy ready to defend his compatriots.

“He is a national hero and comes across as being decent,” said Andreas Umland, assistant professor of European studies at the Kyiv Mohyla Academy.

Klitschko made his first foray into politics during the country’s 2004 Orange Revolution, the mass protests that led to the annulment of Yanukovych’s fraud-tainted presidential victory and ushered in a pro-Western government. After winning a fight in the United States, Klitschko flew to Kiev and appeared in the heart of those protests wearing an orange scarf, the symbol of the revolution.

Next to him stood his brother, Wladimir Klitschko, now 37, another heavyweight world boxing champion who is engaged to the American actress Hayden Panettiere, star of the TV series “Nashville.”

Klitschko has three children with his wife, Natalia, a former model who recently started a singing career.

After two failed attempts to be elected mayor of Kiev, Klitschko entered national politics last year when his pro-Western party — named Udar (Punch in English) — finished a strong third in the parliamentary election running on a reform and anti-corruption platform. He was able to capitalize on popular anger with Yanukovych, who put Ukraine on an authoritarian path, and with voters’ disillusionment with the Orange leaders, now in opposition, including Tymoshenko.

A year before the 2012 election, Tymoshenko was jailed for abuse of office, charges the West considers politically motivated. The pro-Western Tymoshenko has been Yanukovych’s biggest political rival for years.

Klitschko’s mother was a school teacher and his father an army pilot whose job took him to remote military bases across the Soviet Union and Eastern Europe. Klitschko was born in 1971 in Kyrgyzstan, then part of the Soviet Union.

He said he embraced Western values while training in Germany and the United States for matches, and he wants to bring those values home to Ukraine.

“Those people who are in politics (now) do not make it their goal to change the country,” Klitschko said, towering over a reporter at 6 foot, 7 inches. “They are simply plundering the country.”

Unlike many Ukrainian politicians and businessmen who are accused of making their fortunes in shady privatization deals and business wars in the tumultuous post-Soviet years, Klitschko’s millions come from a transparent source — the boxing ring.

An opinion poll in September predicted that Klitschko would get 15.5 percent of the votes in the first round of a presidential election, compared to Tymoshenko’s 13.2 percent. Yanukovych would get 19 percent, but he would lose to Klitschko in a run-off, according to the Razumkov Center poll of 2,010 respondents. It had a margin of error of 2.3 percentage points.

Klitschko’s political star has only risen since then.

In October, Klitschko announced that he would run for the presidency in early 2015, even though parliament, dominated by Yanukovych’s allies, passed a law that sought to bar Klitschko from running on the grounds that he had spent several years in Germany and paid taxes there.

Klitschko was appalled, calling Ukrainian politics a dirty business, unlike anything he had seen in boxing.

“It’s impossible to compare them because in boxing there are rules. In Ukrainian politics, the rules are absent,” Klitschko said.

Klitschko has kept his two careers separate — never joining other Ukrainian lawmakers in the frequent bloody fights that have marred parliament.

“Physical force plays no role in politics. The power of thought is much stronger,” Klitschko said.

How good are Ukrainian lawmakers at throwing punches, anyway?

“If you judge this from the standpoint of (my) profession, they don’t have any talent,” Klitschko said.