Former Prime Minister Benazir Bhutto was one of three Pakistani leaders considered key to the country's national elections in January.
Ms. Bhutto, former Prime Minister Nawaz Sharif and current President Pervez Musharraf lead the country's three strongest political parties - and all three have a long history of jockeying for power.
Ms. Bhutto's father, Zulfikar Ali Bhutto, served as president and prime minister of Pakistan at two different times in the 1970s. He was later deposed in a military coup and hanged in 1979 by military ruler Zia ul-Haq.
Ms. Bhutto was first elected prime minister in 1988. By 1990, she was dismissed by the president because of corruption allegations.
Nawaz Sharif, who won the election to replace her as prime minister in 1990, was briefly ousted for similar corruption charges, but later returned to office. Following political controversy over the corruption allegations, he resigned in 1993. Ms. Bhutto then won re-election the same year, and served until 1996, when she was again forced to step down because of corruption allegations. Ms. Bhutto went into exile in 1998.
Mr. Sharif returned to power in 1997 elections. In 1998, his relations with the military became strained after a failed military escalation in Kashmir. He removed General Pervez Musharraf as army chief, but the plan backfired and General Musharraf instead launched a bloodless military coup.
Mr. Sharif was convicted on corruption and other charges in 2000 and sent into exile in Saudi Arabia.
President Musharraf has ruled the country ever since his 1999 coup. By mid-2007, President Musharraf's popularity was floundering and he faced pressure from western governments to promote democratic reforms. He stepped down as military chief, pledged to hold free and fair national elections and reached out to both Ms. Bhutto and Mr. Sharif to clear the way for their return.
Some information for this report was provided by AP and Reuters.