His message of cracking down on corruption and standing up to the US has found new resonance at a time when Pakistanis are fed up with the country's chronic insecurity and economic malaise.
Imran, 59, entered politics 15 years ago when he founded Pakistan Tehreek-e-Insaf, or the Movement for Justice party, but has struggled to translate his fame into votes. His political fortunes shifted in October when he drew over 100,000 people to a rally in the eastern city of Lahore. Since then, Imran has attracted many politicians to his party, including several prominent figures.
"I came to support an honest politician who quit his lavish life for the betterment of downtrodden people," said 29-year-old Afghan Waqar at Sunday's rally, standing among a sea of people enthusiastically waving the green, red and white flag of Khan's party. Waqar said it was the first rally she has ever attended, a sign of Imran's ability to attract potential new voters who had all but given up on Pakistan's political system, which is widely viewed as corrupt and not responsive to the needs of average Pakistanis.
Javed Odho, a police officer, estimated there were 100,000 to 150,000 people in the crowd. The event was held outside Imran's traditional support base in Punjab province, where Lahore is the capital. Karachi is Pakistan's largest city and is the capital of Sindh province. Imran has been especially popular with the country's urban middle class youth, and many of the people at the rally were young Pakistanis wearing Western clothes.
Two prominent politicians who have joined Imran's party in recent months include former Foreign Minister Shah Mahmood Qureshi, who had a falling out with the ruling Pakistan People's Party, and Javed Hashmi, who was a key member of the main opposition party, Pakistan Muslim League-Nawaz.
Imran's rising popularity could be a concern for the US, given his harsh criticism of the Pakistani government's cooperation with Washington in the fight against Islamist militants.
Despite Imran's rising popularity, it's unclear how much he can shake up the political scene in the next national elections in 2013. Both the PPP and the PML-N have strongly entrenched bases of support that will be difficult to challenge.
It's also unclear exactly what Imran would do if he did win significant political power. He has yet to offer many specifics about how he would fix problems like corruption.
