Khan himself has been accused of enjoying the covert support of Pakistan's powerful military, which has ruled it directly or indirectly for most of the last 70 years.
It would be a historic win and mark the end of a long, winding road to power. Khan, 65, would break the stranglehold of Pakistan's tarnished "status quo" political parties in what would only be its second democratic transition.
Campaigning on a populist, anti-corruption ticket, his Pakistan Tehreek-e-Insaf (PTI), or Pakistan Justice Movement, seeks an end to decades of what it calls the Sharif and Bhutto families' misrule.
In some ways, Khan personifies the crippling contradictions and quest for identity that have hampered Pakistan since its creation in 1947.
In the 1990s, he had ostensibly turned his back on Western "decadence" and the ruling class he came from, instead campaigning for the "masses" and national Islamic pride.
But he has become a wildly popular figure among ordinary Pakistanis, setting up cancer hospitals that treat the poor and wading into the murderous mire of Pakistani politics.
After years as the country's political third man, his muscular charisma and anti-corruption mantra finally caught the imagination of young and middle-class Pakistanis. At the 2013 elections, the PTI broke the duopoly of the main parties. Khan was instrumental in the dismissal last year of former prime minister Nawaz Sharif, jailed this month for corruption-related charges.
Yet, Khan has exposed himself to criticism that he has compromised his vision and tipped his cap to his own, and Pakistan's, worst conservative instincts. Khan's support for the death sentence for those convicted under Pakistan's controversial blasphemy law, and legislation persecuting the country's Ahmadi community as heretics, has discomfited some even among his own ranks.
Sharif claims Khan's campaign against him was conducted in tandem with the army, and that military intelligence officers have pressured his candidates to switch allegiance to the PTI.
If Khan conquers, he will be given a hero's welcome by his loyal fans, but perhaps his hubris and burning desire to become Pakistan's first elected prime minister to fulfil a full tenure in office will blind him to the risk of suffering the same fate as previous incumbents.
- Telegraph Group Ltd