A hero to millions across the cricket-obsessed nation for winning Pakistan its only World Cup in 1992, the 60-year-old has sporting prowess, rugged good looks and international celebrity in a country sadly lacking glamour.
He has electrified the campaign, addressing enormous crowds and galvanising young voters and an urban middle class fed up with the same old politicians who have ruled for decades on the back of family wealth.
To his detractors, he is a dangerous appeaser of the Taliban, a Muslim conservative weak on women's rights and a naive figure who doesn't understand that America's war against Islamic extremists is also Pakistan's war.
Yet even commentators who long scoffed at him as a political lightweight are now reassessing his chances after a campaign which in the absence of a strong showing from the outgoing Pakistan People's Party (PPP) has looked like a two-horse race between him and opposition leader Nawaz Sharif.
"This is a revolution taking place," he told AFP in an interview on the campaign trail in Punjab, the political backbone of Pakistan which elects a little over half the seats in the national assembly.
Khan charge was slowed on Tuesday when he was hurt in a fall at an election rally, but the hospital treating him said that although he injured his head and back and must rest for a week, the damage was not serious.
And hours after the accident, he made a televised statement from his hospital bed urging people to vote for his party in Saturday's polls.
Khan's campaign slogan is Naya Pakistan -- New Pakistan.
The message is simple: the parties that have governed for the past two decades have failed and it is time to try something else: time to pay tax, end corruption, fix the power crisis and stand up to America.
His vocal opposition to US drone strikes targeting the Taliban and al Qaeda has also struck a chord with a deeply anti-American populace.
His face is plastered all over billboards, TV adverts and his Pakistan Tehreek-e-Insaaf (PTI) party has run a strong internet campaign with a stylish website, securing @ImranKhanPTI more than half a million followers on Twitter.
He has promised a "tsunami" -- a landslide victory that would carry him to power. Few expect him to win. Still fewer expect him to make good on his promises, but the question on everyone's lips is how well will he do?
Can he pip the PPP into second place? Can he even beat the front-runners, the Pakistan Muslim League-N, widely expected to form the next government?
"Even now it doesn't seem possible. Logic suggests it simply can't happen," wrote journalist Cyril Almeida in Dawn newspaper.
"But then... but then there is Khan, tearing through Punjab and KP (northwestern Khyber Pakhtunkhwa province), drawing monster crowds; the energy palpable, the voter real, the possibility ever-growing."
Born on November 25, 1952 in Lahore into a comfortable family with origins in the Pashtun northwest, Khan was educated at Aitchison College, the Eton of Pakistan, boarding school in England and then Oxford University.
He became one of the world's greatest ever all-rounders -- a fearsome fast bowler and dangerous batsman -- whose finest hour came at the 1992 World Cup, where at the age of 39 he led an inexperienced team to the World Cup title.
Off the pitch, he had a string of socialite girlfriends and frequented exclusive nightclubs in London until he married Jemima Goldsmith, the daughter of the French-British tycoon James, in 1995.
She converted to Islam and the couple moved in with his family in Lahore.
They had two sons but divorced in 2004, allegedly over the difficulties Jemima faced in Pakistan, where she was hounded for her family's Jewish anestry and his obsession with politics.
Khan founded PTI in 1996. He won one seat for the party in the 2002 election held under military ruler Pervez Musharraf and boycotted the 2008 elections.
He is also known for his philanthropy. He founded the best cancer hospital in the country, which provides free care to the poor, and set up a college that awards British university degrees in Mianwali, his family's home town.
Politics is more than a game, cautions his chief rival Nawaz Sharif, even as his opponents nervously watch over their shoulders the rise of the cricketing legend.