Much has changed - and remained the same - since the 2004 presidential election and Orange Revolution. Ukrainians voted on Sunday for a new president in a run-off between Prime Minister Yulia Tymoshenko and opposition leader Viktor Yanukovich, but the prospect of post-election unrest threatens any quick return to stability, analysts say.

Following is a timeline of political events since the mass protests brought pro-Western politicians to power in 2004.

Jan. 23, 2005 - Viktor Yushchenko is sworn in as president after street protests in November and December against a rigged election won by then-Prime Minister Viktor Yanukovich.

-- Yulia Tymoshenko, Yushchenko's "Orange Revolution" ally, is named prime minister within days.

Sept. 8 - Yushchenko dismisses Tymoshenko's government after infighting. Yuri Yekhanurov, a presidential ally, replaces her.

March 26, 2006 - Yanukovich's Regions Party emerges as the largest party in a parliamentary election with 186 of 450 seats, but is outnumbered by the combined "orange" score of 243. Orange groups, however, fail to form a coalition after months of talks.

July 18 - A coalition made up of the president's opponents proposes Yanukovich as prime minister. He is approved a month later after promising not to reverse pro-Western policies.

Jan. 12, 2007 - Yanukovich supporters pass law to reduce Yushchenko's control of the government, a blow to his authority.

April 2 - Yushchenko dissolves parliament, calls election, leading to months of turmoil.

Sept. 30 - In a new election "Orange" parties win a majority of 227 seats -- one more than needed to win most votes in the 450-seat chamber.

Dec. 18 - Parliament approves Tymoshenko as prime minister with 226 votes, the minimum number required to take office.

Aug. 18, 2008 - President's office says Tymoshenko betrays national interests by not backing Georgia in its conflict with Russia.

Sept. 3 - Our Ukraine, Yushchenko's allies, quit "Orange" coalition after denouncing joint vote by Tymoshenko's bloc and Yanukovich's party. The president threatens to call an election.

Nov. 6 - The IMF approves a $16.4 billion loan programme for Ukraine to ease strains from the global financial crisis. Days later it receives its first tranche worth $4.5 billion.

Jan. 20, 2009 - Russian gas reaches Europe via Ukraine for the first time in two weeks after Moscow and Kiev end a prices and debt row that cut supplies to about 20 European countries. Yushchenko says the deal clinched by Tymoshenko is a "defeat".

March 3 - Parliament sacks Foreign Minister Volodymyr Ohryzko, a Yushchenko ally, citing his aggressive stance against Russia and for bungling a territorial dispute with Romania.

June 5 - Parliament dismisses another Yushchenko ally, Defence Minister Yuri Yekhanurov over allegations of corruption in the ministry.

Oct. 30 - Yushchenko says he signed a bill raising minimum wage by over 20 percent by the end of 2010 at an extra cost of $10 billion. The IMF suspends lending as the measure breaches government promises to keep the budget deficit under control.

Dec. 9 - Russian President Dmitry Medvedev says it would be "irresponsible" to amend gas supply contracts with Ukraine, in a sign Moscow will offer no more concessions to its neighbour on gas payments. Yushchenko had asked Russia in November to change the gas supply deal, saying it was too onerous for Ukraine.

Jan. 17, 2010 - Yushchenko is defeated in presidential election. A runoff is set between Tymoshenko and Yanukovich.

Feb. 3 - Tymoshenko accuses Yanukovich of preparing to rig the poll through late changes to election rules. The next day she says she will call people onto the streets if she considers procedures and vote-counting are rigged in the Feb. 7 runoff.