Main players in Ukraine's party politics

Yushchenko, Prime Minister Yulia Tymoshenko and opposition leader Viktor Yanukovich have dominated politics since the 2004 "Orange Revolution" - mass rallies against a rigged presidential election in which Yushchenko was eventually declared the winner.

Yanukovich was the Moscow-backed candidate in 2004 whose initial victory sparked the protests, led by Yushchenko and Tymoshenko. Political turmoil has since generated speculation that either the president or premier could join forces in parliament with Yanukovich.

Opinion polls vary widely but most have Tymoshenko and Yanukovich vying for the lead with just over 20 percent each. Yushchenko and his party trail in single figures, with some surveys crediting Our Ukraine with about 5 percent.

* YULIA TYMOSHENKO - Prime Minister (46):

-- The former gas tycoon turned social crusader was allied with Yushchenko during the 2004 revolution. Her impassioned speeches kept hundreds of thousands on the streets for weeks.

-- Yushchenko named her his first prime minister in 2005 but the honeymoon was shortlived -- he sacked her after eight months, with each side accusing the other of corruption. She was appointed a second time in December, 2007. -- Her policies include billions in compensation for depositors who lost Soviet-era savings, price controls on food to bring inflation down, calls for review of opaque privatisations, high social spending.

-- In her first tenure as premier fiery rhetoric about corruption in the gas sector pushed relations with Russia to a low and the cost of imports doubled soon after. Her opponents now accuse her of seeking Moscow's favour to win its support for a likely bid in the next presidential election in 2010. -- Her bloc is made of several parties whose heartland support is in the west of the country.

* VIKTOR YUSHCHENKO - President (54)

-- The former central bank chief and prime minister was poisoned by dioxin in the 2004 presidential campaign. His face was disfigured and he underwent a long series of operations.

-- Yushchenko has made membership of the NATO military alliance and the European Union policy cornerstones. Yushchenko is deeply religious and frequently cites Ukrainian history, particularly centuries of failure to achieve statehood.

-- Popular support for Yushchenko after his victory in the re-run 2004 election ebbed away as his aim of turning Ukraine into a modern state with a Western orientation gave way to infighting and indecision.

-- His credibility dropped further after he agreed to appoint Yanukovich prime minister in 2006 -- subject to a deal that was supposed to leave pro-Western policy goals intact. Support for Yushchenko now stands at less than 10 percent.

-- His party, Our Ukraine, has a support base in western Ukraine.

* VIKTOR YANUKOVICH - Opposition leader, former PM, (57):

-- The Moscow-backed candidate was initially declared the winner of the rigged 2004 presidential election, but lost the re-run of the poll ordered by the Supreme Court. He made a remarkable comeback in 2006 when his party finished first in a parliamentary poll and Yushchenko appointed him prime minister after "orange" parties failed to form a coalition.

-- Hailing from industrial eastern Ukraine, his Regions party is seen as representing the business interests of heavy industry oligarchs.

-- Yanukovich has warmer relations with Russia and is unenthusiastic about Yushchenko's plans to seek fast-track NATO membership. But like virtually all politicians in Ukraine, he supports further integration with the European Union.