Timeline: Five years of Polish politics under Kaczynski twins

(Reuters) - Jaroslaw Kaczynski is running for Poland's presidency in a run-off presidential election on Sunday, three months after the death of his identical twin brother President Lech Kaczynski in a plane crash in Russia.

The conservative Kaczynski twins have been important players in post-communist Polish politics, though opinion polls suggest Jaroslaw Kaczynski will be defeated in the run-off by the ruling Civic Platform party's candidate, Bronislaw Komorowski.

Jaroslaw Kaczynski, a former prime minister, leads the right-wing main opposition party Law and Justice (PiS).

Below is a timeline of key events involving the Kaczynski twins over the past five years.

October 23, 2005 - Conservative Warsaw Mayor Lech Kaczynski beats free market champion Donald Tusk in presidential election.

-- Conservative Law and Justice party wins the parliamentary election and Kazimierz Marcinkiewicz becomes prime minister.

May 5, 2006 - Law and Justice forms a coalition government with the ultranationalist League of Polish Families and rural-based populist Self-Defense party.

July 14 - Prime Minister Jaroslaw Kaczynski is sworn in by his twin brother to replace Marcinkiewicz, who resigns.

September 21 - Kaczynski kicks Self-Defense out of the government, calling its leader Andrzej Lepper a "rabble rouser," but a deal is reached later to save the coalition.

November 23 - Poland vetoes key agreement between EU and Russia, demanding an end to Moscow's embargo on its food products.

December 1 - Junior coalition party League of Polish Families comes under fire after a newspaper publishes photographs of members of its youth organization giving Nazi salutes.

December 4 - Newspaper publishes accusations against senior Self-Defense figures, saying they gave women party workers jobs in exchange for sex.

July 9, 2007 - Prime Minister Kaczynski expels Lepper from the cabinet over a corruption investigation, prompting weeks of bitter infighting.

August 13 - Prime Minister Kaczynski sacks ministers from junior coalition parties, tearing the government apart.

September 7 - Parliament votes to end its term two years early, making an election necessary.

October 21 - Kaczynskis' Law and Justice party loses parliamentary election to opposition Civic Platform. Future prime minister Donald Tusk promises to improve ties with Russia.

August 12, 2008 - President Lech Kaczynski travels to the Georgian capital, Tbilisi, to show solidarity during the small ex-Soviet republic's brief war with Russia.

November 21, 2009 - Prime Minister Tusk says he aims to strip President Kaczynski of his veto powers in a constitutional revamp designed to end institutional conflicts that he says have blocked important reforms.

-- Kaczynski, Tusk's arch rival, has vetoed a number of government bills, including media, health and pensions reforms, citing their impact on ordinary workers.

January 9, 2010 - President Lech Kaczynski criticizes the government for prolonging gas negotiations with Russia and deepening Poland's already-heavy reliance on Russian gas.

April 10 - President Kaczynski, his wife and 94 others, mostly top officials, die when their Tupolev plane crashes in thick fog near Smolensk airport in western Russia. They were planning to mark the 70th anniversary of the massacre of Polish officers by Soviet forces in Katyn forest during World War Two.

-- Bronislaw Komorowski automatically takes over as Poland's acting president in his capacity as speaker of parliament. Komorowski has already been declared the presidential candidate of the governing party, Tusk's Civic Platform.

April 26 - Jaroslaw Kaczynski says he will be the candidate of his Law and Justice party in the presidential election.

June 20 - Kacyznski wins a bigger-than-expected 36.5 percent of the vote in the first round of the election, five percentage points behind Komorowski.

July 4 - Second and decisive round of presidential election.