KIEV, Ukraine - During the traumatic campaign, he was poisoned with a powerful toxin, ignored by the major media, defeated by a rigged ballot and fiercely opposed by top government leaders.
But if and when he is inaugurated president of Ukraine, Viktor A. Yushchenko may find that his troubles have just begun.
Yushchenko has pledged not only to clean up this country's pervasive public corruption and strengthen the rule of law, but he also has promised to create 5 million jobs in this nation of 48 million people, raise pensions for the elderly by 50 percent and swiftly integrate Ukraine into Europe.
Yet he is poised to claim the presidency at a time when the country is preparing to switch from a presidential to a parliamentary system, which will sharply reduce the clout of the office for which Yushchenko fought so long and hard.
Yushchenko said Sunday that he might try to repeal the change to a parliamentary system. But analysts say this could prove impossible because it would require the support of 300 of 450 parliamentary deputies. Yushchenko has the support of only about 120 deputies.
"He will not be able to put in practice most of what he promised," predicted Vladimir Malinkovich, a scholar with the International Institute for Humanitarian and Political Studies in Kiev.
Yushchenko declared victory yesterday, with a lead of 52 percent to 44 percent after almost all the votes were counted.
His opponent, Prime Minister Viktor F. Yanukovych, who favored strengthened ties with Russia, claimed from the start that Sunday's Supreme Court-ordered rerun of the Nov. 21 elections was illegal. He refused to concede defeat yesterday and announced through a spokesman that he would challenge the outcome, either in the Central Election Commission or in court.
Both sides accused the other of election law violations, although observers reported no evidence of the systematic fraud that caused the court to throw out last month's ballot. The Central Election Commission has 15 days to declare a formal victor.
Western analysts see the Ukraine vote as more than just another election. It was, they say, a struggle to complete what Stanford political scientist Michael A. McFaul calls one of the former Soviet Union's "unfinished revolutions" and rid the nation of the Soviet legacy of corruption and cronyism.
But Yushchenko, some analysts say, must decide whether he wants to impose reform from above, as a strong president, or work within a parliamentary system that establishes the principles of political pluralism and a balance of power.
Malinkovich and others say Yushchenko should avoid the temptation to concentrate power in his own hands. Otherwise, Malinkovich said, "in Yushchenko we will have a Ukrainian Putin, and that is all."
Under departing President Leonid D. Kuchma, the president wielded enormous power. He hired and fired prime ministers at will, controlled economic policy and set the domestic and foreign political agenda.
Under the constitutional reforms adopted by parliament on Dec. 8, in exchange for reform of the election laws, the president will in the future appoint only the ministers of defense, of foreign affairs and the chief of the security agency, the SBU, the successor agency to the KGB.
The prime minister, meanwhile, would control the economic and domestic agenda and appoint regional governors. Crucially, the prime minister could not be removed by the president without parliament's approval.
The reforms won't take effect until Sept. 1, at the earliest. But Vladimir Polokhalo, a political scientist with the National Academy of Sciences of Ukraine, said that if Yushchenko takes office, he will serve as little more than an interim leader.
"The presidential election is just a transition between the old government and the parliamentary elections in March 2006," he said. "At that time, Ukraine will form a real government, with the prime minister as its leader."
Ukraine's next parliament might or might not be sympathetic to Yushchenko's goals. Today, analysts say, the legislature is controlled by business tycoons, called "oligarchs."
Among them is President Kuchma, whom Polokhalo described as the leader of a group of oligarchs based in the industrial city of Dnipropetrovsk in eastern Ukraine. "He may be the richest man in Ukraine," Polokhalo said.
Most urgently, Yushchenko needs to make peace with the restive Russian-speaking regions in the east, where many voters supported Yanukovych and now feel robbed of victory. These regions are not likely to try to split with Ukraine and join Russia, as they have sometimes threatened, analysts say. But the regions could decide to systematically block Yushchenko's reform programs.
The pro-Western politician must also swiftly repair relations with the Kremlin. Russia is a major trading partner, and Russian companies have huge stakes in many of eastern Ukraine's mining, refining and manufacturing enterprises.
Ukraine's economy is booming after years of stagnation. But the average wage here is still just $80 a month, less than half of that in Russia.
Yushchenko's victory represents more than just an embarrassment for Russian President Vladimir V. Putin, who embraced Yanukovych as an ally. It could wreck Putin's hopes for a political and economic alliance among former Soviet states, centered in Moscow.
There are signs the Kremlin is seeking to reach out to Yushchenko. Aleksandr Veshnyakov, the chairman of the Russian Central Elections Commission, said he had no reason "to question the general outcome" of the Ukraine vote, the wire service Interfax reported.
Mikhail Spektor, Yushchenko's representative in Moscow, told reporters that Yushchenko sees Russia as a strategic partner and pledged to be "a guarantor of stability" for Russian investors in the country.
But other analysts said the Kremlin is still befuddled by Yanukovych's defeat, which it regards as having been engineered by the United States. "The Kremlin is perplexed, surprised and lost," Malinkovich said.
On a personal level, Yushchenko will be at the center of what is likely a politically charged investigation into his dioxin poisoning and reportedly faces months of medical treatments - perhaps including plastic surgery.
If Yushchenko decides to accept the new parliamentary system, he will need to create almost from scratch a full-fledged political party to carry his banner.
Currently there are more than 130 tiny Ukrainian political parties, most of them little more than vehicles for the ambitions of individual politicians.
Under the constitutional reforms, a party must win at least 3 percent of the vote in order to win a share of the seats in the parliament. These parties must be registered with the government by March 1.