Khan, who heads the Pakistan Tehreek-e-Insaf or Movement for Justice Party, was greeted Sunday in Karachi by an estimated 100,000 people, whom he promised to eliminate corruption and help the people prosper.
Pakistan's Nation newspaper said Khan's party had waited 15 years for a candidate who could energize the people of the country, which has convulsed from monumental economic, law and order, and political problems.
The report said Khan has not yet spelled out what changes he proposes and how to implement them, but that has not stopped the crowds.
The mammoth receptions have only helped boost Khan's stature as a new force on the country's political scene.
The 59-year-old Khan, who as captain helped make Pakistan's cricket team into a formidable opponent, remains immensely popular with people.
His fresh foray into politics comes as the government of President Asif Ali Zardari butts heads with the powerful military, prompting rumors a coup is possible. Such talk, however, has been dismissed by the country's army chief and the country's chief justice.
The Karachi rally was in honor of the birthday of the late Mohammed Ali Jinnah, the founder of Pakistan, the Los Angeles Times reported.
The Times quoted Khan as saying if his party came to power after elections scheduled for 2013, he would ensure the rule of law is applied to all and would work to eradicate the taint of corruption at all levels of society.
"We will create a police force independent of political influence, based purely on merit," Khan told the crowd, adding: "We will control corruption. God willing, we will end corruption in 90 days."
CNN reported Khan also opposes U.S. drone strikes in his country.
Among prominent people from other political parties that Khan's movement has attracted include former Foreign Minister Shah Mehmood Qureshi and Javed Hashmi, one of the leaders of the main opposition party.
The Times said Khan's party is likely to at least become a major opposition force in the future.