A look at several key players in Pakistan's national election:
NAWAZ SHARIF: The head of the main opposition party in recent years, the Pakistan Muslim League-N, is considered the front runner in the election and hopes to become prime minister for the third time. His party, which appeals to a pro-business base and is strongest in central Punjab province, is considered the main rival to the Pakistan People's Party to form the next government. Sharif was ousted as prime minister in a bloodless coup in 1999 by then-army chief Gen. Pervez Musharraf and was sent into exile the following year. He returned to Pakistan in 2007 to lead his party in the 2008 elections, which was won by the PPP.
IMRAN KHAN: A Pakistani cricket legend-turned-politician who could have a significant impact on the vote. He founded Pakistan Tehreek-e-Insaf, or the Movement for Justice Party, more than 15 years ago, but failed to gain much traction until 2011. That year he marked his rise as a major political player with a rally that drew more than 100,000 people in Lahore, the capital of Punjab province. Khan has appealed to a largely young, urban constituency tired with the current crop of politicians and the corruption that plagues the system. It's unclear whether he can win enough seats to form the next government, or simply steal key votes from the PML-N and the PPP, especially in Punjab. That could affect who wins. He could win more votes out of sympathy after a freak accident this week at a political rally in which he fell 4.5 meters (15 feet) off a forklift, fracturing three vertebrae and a rib.
PRESIDENT ASIF ALI ZARDARI: The president rode to power on a wave of sympathy following the 2007 assassination of his wife, former Prime Minister Benazir Bhutto, but his tenure has been turbulent and he has long been plagued by allegations of corruption. Zardari is not running in Saturday's vote but as a former head of the Pakistan People's Party, which led the last government, he is a central figure in the party's electoral future. His unpopularity and anger over the performance of the government during its five-year term is likely to hurt the party's chances in the vote. The economy is stuttering, energy shortages plague the country and Taliban militants continue to stage deadly attacks.
—BILAWAL BHUTTO ZARDARI: The only son of the president and his late wife, he was set to carry the torch for the Bhutto family political dynasty in Pakistan but has largely been absent in this election. His grandfather, Zulfikar Ali Bhutto, founded the PPP and served as the country's president and prime minister. Zardari is too young to participate in the election — the minimum age is 25 — but he had been expected to play a key role in rallying voters. However, Taliban threats meant the Oxford-educated youth spent almost no time on the campaign trail, leaving the PPP without a central figure to rally around.