His newly-formed Justice Movement party will contest the elections on 3 February for the National Assembly, though Mr Khan will have only the slimmest chance of winning. The vote is being called early, after the President, Farooq Leghari, on Tuesday dismissed Benazir Bhutto's government for suspected corruption.
"It's true I never wanted to come into politics, but we feel it's time to protect the people from this corrupt mafia," Mr Khan said. "The other politicians only select people for government posts who are their relatives or sycophants." Mr Khan said he supported the removal of Ms Bhutto. The country had to be "salvaged from sordid opportunism".
The cricket star is delaying the start of his campaign until after he returns from Britain where his wife, Jemima, the daughter of multi-millionaire Sir James Goldsmith, is expecting a baby "at any moment". Mr Khan denied that having a foreign wife (Jemima, at 22, is half his age) would hinder his election chances. "Westerners seem to find this very surprising, but my wife has been accepted easily here in Pakistan," he said.
Mr Khan launched his party last spring, when a bomb exploded in the lobby of his cancer charity hospital in Lahore, killing several people and injuring many. He implied that Ms Bhutto's party thugs might have planted the bomb to scare him into ceasing his criticisms of the premier. Soon after, he threw himself into a campaign to have her removed from office. Throughout the past few months, Mr Khan has been travelling doggedly across the country, holding rallies and denouncing Ms Bhutto and her husband, the former investment minister, Asif Zardari, whom he described as the "World Cup winner of corruption".
So far, his rallies have been sparsely attended. Most of his followers are cricket-mad youths, below the voting age. He has an image problem, too. Many Pakistanis see him as honest and courageous but naive. "I know my limitations. But I feel I'm better than the lot of them," he said yesterday. To his advantage, many Pakistanis are so disheartened with Ms Bhutto's Pakistan People's Party and the opposition Pakistan Muslim League of the former prime minister, Nawaz Sharif, that they might opt for Mr Khan.
However, rural Pakistan is still in the grip of feudal landlords and tribal chieftains. It is they who can deliver thousands of votes, and without their support, without playing the game of influence-peddling, Mr Khan may end up with his reputation unstained but with only a few seats in parliament.
The country's new caretaker Prime Minister, Meraj Khalid, 80, is refusing to move into Ms Bhutto's grand, official residence, preferring to stay in his two-room bungalow. Pakistanis, long accustomed to Ms Bhutto's style of Moghul hauteur, were stunned to see a newspaper photograph yesterday of Mr Khalid tottering his way to an economy-class seat on a flight to Lahore.