FACTBOX: Candidates for Pakistan's presidential vote

(Reuters) - Pakistan's three main political parties have submitted nominations for a September 6 presidential election for a replacement for Pervez Musharraf, who stepped down last week under threat of impeachment.

Under Pakistan's constitution members of the country's four provincial assemblies and the two-chamber national parliament elect the president.

Here are some facts about the three main presidential candidates:

ASIF ALI ZARDARI

* Former prime minister Benazir Bhutto's widower and political successor, Zardari was thrust into the centre of politics by his wife's assassination on December 27, and then to the centre of power after their Pakistan People's Party won the most seats in a February 18 election.

* Born in the southern province of Sindh to a land-owning family, the telegenic Zardari, 55, has long been controversial.

* He served as a minister in his wife's second government in the 1990s, and was a senator until 1999, but was accused of getting kickbacks on government deals and earned the nickname "Mr Ten Percent".

* Despite spending altogether 11 years in prison on charges of corruption and murder, Zardari, who has denied all accusation and was never convicted, was released on bail in 2004.

* Last year, Musharraf granted an amnesty to Bhutto, Zardari and other party leaders from graft charges under a power-sharing deal with Bhutto.

* He married Bhutto in 1987 and they had three children: two girls and a boy.

* Analysts say Zardari should have enough electoral college votes to win.

SAEEDUZZAMAN SIDDIQUI

* Siddiqui is a former judge, nominated for the post of president by the party of former prime minister Nawaz Sharif, the Pakistan Muslim League (Nawaz).

* The soft-spoken Siddiqui was a Supreme Court judge when he ruled in favor of then Prime Minister Sharif in a confrontation with the judiciary in 1997.

* Siddiqui lost his job as a Supreme Court judge after then army chief Musharraf overthrew Sharif in a 1999 coup and demanded an oath of allegiance from members of the judiciary.

* Born in 1937 in Calcutta, in what was then British-ruled India, Siddiqui moved to Pakistan with family in 1956.

MUSHAHID HUSSAIN SAYED

* Sayed has been nominated by the Pakistan Muslim League which backed Musharraf and ruled under him.

* Sayed, a former journalist, served as information minister in Sharif's cabinet until the government was forced from power by Musharraf's 1999 coup.

* He was detained for more than a year after the coup but upon his release joined the party Musharraf cobbled together to provide him with a base of support, and was elected as a senator.

* He later became secretary general of the so-called King's Party, a moderate face in a conservative party that was defeated in a February 18 general election.

* The son of an army colonel, the astute, affable Sayed studied at Georgetown University in Washington.

(Writing by Kamran Haider; Editing by Robert Birsel and Jerry Norton)