Petro Poroshenko, a 48-year-old billionaire known as the 'Chocolate King' is now the front-runner for the 25 May presidential election in Ukraine, which the new leadership hopes will unite a divided country, amid growing pressure from Russia hostile to its political changes.
Poroshenko, whose chain of confectionery shops puts him in Ukraine's top 10 rich list, received a huge boost at the weekend when popular boxer-turned-politician Vitaly Klitschko pulled out of the race and endorsed him for the presidency.
Even before Klitschko bowed out on Saturday, Poroshenko, a beefy man with a thick shock of grey hair, was well ahead in ratings at 25%, with Klitschko at 9% and former Prime Minister Yulia Tymoshenko trailing with 8.3%.
The development appeared to eclipse Tymoshenko's hopes of profiting from her persecution under the ousted Viktor Yanukovich, including 2-1/2 years imprisoned in a hospital, to win the presidency - a post she has long coveted.
The flamboyant former prime minister and heroine of a previous uprising 10 years ago called the 'Orange Revolution' declared her bid for the presidency last week, saying she too saw herself as the candidate of "Ukrainian unity".
Poroshenko is an experienced politician, having held a variety of portfolios, including that of economy minister, under pro-Western and Moscow-backed administrations.
But late last year, he quickly spotted the changing mood in the country as protests began against Yanukovich's retreat from European integration, and threw his weight behind the pro-Europe 'Euromaidan' movement that forced Yanukovich to flee.
The oligarch, estimated by Forbes to be worth $1.3 billion (approx.. €1 billion), is the owner of Roshen, a Ukrainian chocolate manufacturer and one of the world's top twenty confectionery firms.
Significantly, his retail businesses in Russia have been targeted, as Moscow applies pressure to counter Ukraine's drive towards the West.
Russian riot police last week took control of a Roshen factory in the city of Lipetsk as part of an investigation into the company's affairs, the Ukrainian government said.
Clashes with the Kremlin
Even before the Euromaidan protests took off in November, after Yanukovich walked away from a trade deal with the European Union, Poroshenko clashed publicly with a Kremlin official at a conference in Yalta, over trade pressure being applied by Moscow.
Then, when the Euromaidan revolt gathered pace, he was the only oligarch to back the protesters, appearing with opposition leaders on Independence Square, or the Maidan, launchpad of the uprising.
Crucially, he devoted his 5th Channel TV station to coverage of the protests, turning it into a conduit for interviews and opinions which state-owned channels shunned.
As the crisis grew in Crimea, he further boosted his 'street cred' by flying to the peninsula in a personal initiative to try to speak to pro-Russian forces as they took control. But he met a hostile reception and flew back to Kyiv the same day.
His past government experience, and his huge range of business contacts should help Poroshenko, if he secures the presidency, to bridge the east-west divide in the country.
The support of Ukraine's powerful tycoons, such as steel and chemicals magnate Rinat Akhmetov, is important, since many are located in the east of the country where the population is largely Russian-speaking and more susceptible to the Russian script about developments in Ukraine.
Though Poroshenko now has the clearest chance of securing the presidency, commentators warn of the unpredictable mood in the country following the trauma of the past four months, in which 100 people died violently on the streets of Kyiv, apart from Russia's annexation of Crimea, which the new leaders never appeared to foresee.
"Poroshenko must be very careful. At the moment, the national mood is in his favour, and the most important thing for him is not to do anything that could negatively influence public opinion," said Volodymyr Fesenko of the Penta think tank.
Announcing his decision to run for president in his base of Vinnytsia in central Ukraine, Poroshenko voiced defiance over the Russian takeover of Crimea and called for the creation of an effective, modern armed forces.
"The Ukrainian army will not give up an inch of Ukrainian land," he declared.
Need for unity
Given the gravity of Ukraine's situation, Poroshenko made a direct appeal to Tymoshenko to drop her challenge for the presidency and unite behind him - or at least run a contest that does not fracture the political unity of the country.
"Yulia Vladimirovna will not be our political opponent ... We would regard it highly if Yulia Vladimirovna supported our initiative today," Poroshenko said.
So which way will she jump?
Tymoshenko's years in prison under Yanukovich, and the almost iconic status she enjoys among followers in west and central Ukraine, seemed initially to guarantee her political comeback.
But she received a muted response from the Maidan - the people's forum and centre of the Euromaidan protests that forced Yanukovich to flee - when she was brought there in February. in a wheelchair shortly after her release from detention.
Tymoshenko was the victim of a swing against her and other established figures of a discredited political class.
Many remember her as the 'gas princess' of the 1990s when, long before becoming prime minister, she made a fortune as a gas intermediary during the government of Pavlo Lazarenko. Lazarenko himself was convicted and jailed in the United States in 2006 for money laundering and other offences.
A fiery speaker who is widely perceived as being divisive and often blatantly populist, Tymoshenko is clearly trying to adapt her style to meet an electorate that has become disenchanted with the old political class.
Change of image
She is certainly working to change her public image. Once famous for her elegant couture, Tymoshenko cuts a more sober figure now, wearing darker clothes and eschewing her trademark hair braid in favour of a straighter, more severe hair style.
She appears publicly using a crutch for support - a reminder of the spinal problem she suffered from during her time under prison guard in the town of Kharkiv.
Condemning the Russian annexation of Crimea is an easy cause for a Ukrainian presidential candidate.
But Tymoshenko has more reason than most - being associated in the public mind, rightly or wrongly, with once having enjoyed warm relations with Kremlin chief Vladimir Putin.
This goes back to a gas deal she brokered with Russia in 2009 which the ousted government said saddled Ukraine with an exorbitant price for gas, and which caused her to be jailed for abuse of office under Yanukovich.
Unsurprisingly, Tymoshenko is now going out of her way to try to remedy what she sees as misperceptions.
"I can only say that as long as Crimea is occupied by the Kremlin, Vladimir Putin for me remains enemy No. 1 for Ukraine and I will direct all my forces at defending Ukraine and ending the occupation of Crimea."
She is an old adversary too of Poroshenko, from her time as prime minister. In 2005, she attacked Poroshenko, then secretary of the National Defence and Security Council, alleging his involvement in corruption. The scandal was ended only when the then President Viktor Yushchenko sacked them both.