ISLAMABAD - Imran Khan has been written off before. As a cricketer, he was initially dismissed as having average ability before captaining his team to World Cup glory. For the past 15 years his political party has stumbled from one election humiliation to the next.

Now though, he is convinced his time has come. Riding a tsunami of popular support ahead of elections widely expected next year, he is bracing himself for a campaign of dirty tricks. “During a match there comes a time when you know you have the opposition on the mat. It is exactly the feeling now, that I have all the opposition by their balls,” he said, in an interview with The Daily Telegraph as he travelled to Peshawar for yet another rally on his 59th birthday. “Whatever they do now will backfire.”

Further evidence of Khan’s steepling ascent was on evidence in Karachi, today on Christmas Day, when at least 100,000 people turned out to hear his message that change was sweeping the country. The figure is all the more remarkable as the city is far from Mr Khan’s stronghold of Lahore.

Everything changed in October, when he attracted more than 100,000 supporters to a parade ground in Lahore. The world took notice of a new star in Pakistan’s political firmament, dominated for decades by a handful of the richest families.

Even that rally was almost sabotaged. At the last minute his venue was moved from a modestly sized park to the Minar-e-Pakistan, capable of holding hundreds of thousands of people.

If the switch by city authorities was an attempt to make Khan’s rally appear insignificant it failed badly. Khan expects more of the same. His Lahore headquarters were recently sealed off amid allegations taxes had not been paid.

In 2008, a photograph of a fake £40m cheque apparently from James Goldsmith, billionaire father of Khan’s ex-wife Jemima, surfaced. “They will throw everything at me,” he said. “Last time around, when they panicked, they called Jemima part of a Jewish lobby. She’s Christian, her mother’s Christian, her father was Christian, but because the grandfather was Jewish it became part of a Jewish plot to take over Pakistan.”

Inevitably scrutiny will fall on Khan’s private life. As one of Pakistan’s most famous bachelors he had been expecting Mr Nawaz Sharif’s party to spread malicious rumours – until an American journalist published a book detailing how the opposition leader had offered her an iPhone and asked her to be his “special friend”.

“He can’t really do that now because he knows it will just come back to haunt him,” said Khan roaring with laughter in the front seat of a supporter’s car. “Now they are going after me on tax, but that will look even worse.”

He is also frequently accused of being pro-Taliban and anti-American for his longstanding policy of advocating peace talks in Afghanistan and Pakistan’s withdrawal from the war on terror. But he said the past year, with increasing contacts between American and Taliban leaders, backed his position.

After two hours travelling from Islamabad, his car arrived in Peshawar. Thousands of mostly young men thronged the track ahead, bringing Khan’s small convoy of three cars to halt, as they crowded close.

Inside, his supporters fell silent. In a country known for political assassinations and suicide bombings , Khan is unusual: he does not travel in an armoured vehicle.

Perhaps sensing the unease, he turned to face his nervous passengers.

“There won’t be a suicide attack on this car,” he said with a grin. “They see me as a self-respecting Pakistani nationalist – not an American stooge.”