ISLAMABAD—Former cricket star Imran Khan has been waging his campaign to oust Pakistani Prime Minister Nawaz Sharif for 25 days from a shipping container set in the middle of the tent city inhabited by his supporters.
Though Mr. Sharif has dug in and refuses to resign, Mr. Khan told The Wall Street Journal that he believes victory is near—and that the protests that have paralyzed Islamabad, inflicting heavy economic damage on the country, will go on until then. He also denied charges that he was holding the protests in collusion with the country's powerful military.
"I know winning and losing. I know when I'm winning. It's a matter of time," Mr. Khan said in an interview, after returning to his container from delivering a fiery speech and taking off a sweat-drenched bulletproof vest. "As long as the movement is growing, I'm winning."
Though the crowds attracted by the protests are now much smaller than the million people initially advertised by Mr. Khan and his ally, Islamic cleric Tahir ul Qadri, the 62-year-old former sports star said he is confident that Mr. Sharif will eventually make "one last blunder" in handling the protests and lose power.
"I know he's going to do it sooner or later, as long as I keep the pressure on," said Mr. Khan.
In the meantime, Mr. Khan said, he is staying put in his windowless container, where he holds court in a large leather chair with ballistic shields propped up against the wall and senior party members lining up to wait for their audience.
He sleeps and holds meetings in the container and makes nightly addresses from its roof to a few thousand enthusiastic supporters, who press against coils of barbed wire protecting their leader's shelter and sometimes try to climb the ladder to get in.
Mr. Khan's went into politics 18 years ago after a dazzling cricketing career that made him a national hero, particularly after he led the country's cricket team to its only victory in the game's World Cup in 1992. He didn't contest the 2008 election because former dictator Pervez Musharraf was still in power. It was only in the 2013 election that his Pakistan Tehreek-e-Insaf party became a significant political force, garnering garnered 7.7 million votes in 2013 elections from voters disillusioned with the two largest parties, Mr. Sharif's PML-N and the Pakistan Peoples Party that controlled the previous government, becoming In 2013 Mr. Khan's PTI became the second biggest vote-winner and the third-largest faction in Parliament.
Mr. Sharif, whose party got twice as many votes as PTI and holds a comfortable majority in parliament, denies the rigging allegations but has offered a judicial investigation of the election results in response to the protests. The prime minister has refused to resign, however, and has been backed in that stance by all the opposition political parties except Mr. Khan's PTI.
"The sit-ins are an unsuccessful attempt to derail economic development, but we will continue our journey of progress and prosperity," Mr. Sharif said Monday.
While Mr. Khan's message criticizing Pakistan's other main political parties as corrupt and out of touch with the common voter resonated among many Pakistanis during last year's campaign, critics have attacked him for being soft on the Taliban and for cozying up to the country's powerful military.
The army stepped in after the demonstrations briefly turned violent last month, warning both the government and the protesters to refrain from bloodshed and trying to mediate the standoff. So far, however, the army—which ruled the country for half of its history—has stopped short of imposing its own solution to the continuing crisis.
Mr. Khan said that he is opposed to any outright coup, or to replacing Mr. Sharif with a long-term technocratic civilian government that would be overseen by the military. Mr. Khan also rejected as "a blatant lie" the recent allegation by his party's breakaway president, Javed Hashmi, that he works in collusion with the military, which has long been at odds with Mr. Sharif.
"If I struggle for 18 years, do you think I would do all this to get the army in? The only reason I'm in politics is to get rid of the two parties that have destroyed our country," said Mr. Khan. "I am the only politician who was not raised at the nursery of the military."
Mr. Khan has repeatedly accused Mr. Sharif of stealing the May 2013 election by orchestrating an elaborate conspiracy involving the Election Commission, the judiciary, the interim government appointed to oversee the polling, and a leading news channel. Mr. Khan said he launched the protest after exhausting all legal means of challenging the result.
"I figured out that it is just impossible to beat this mafia, because you can't beat them in an election as they indulge in the most massive rigging," he said. "You cannot go to the courts or Parliament—they are just occupied territory..You have only two ways of dislodging the status quo. One is a bloody revolution, the other is a peaceful one, by mobilizing the masses. There is no third way."
His choice is peaceful protest, he added. Though the protests resulted in three deaths and hundreds of injuries after protesters tried to march on government buildings in late August, the protesters' tent city outside the parliament—modeled on Tahrir Square in Cairo or the Maidan in Kiev— is now peaceful.
Mr. Khan's speeches from atop his container often center on "genuine democracy" and are punctuated with catchy music. Unusually for Pakistan, a large adoring contingent of women among the crowd helps turn the drab square outside parliament into a nightly mixture of political defiance and disco fun.
With government and parliament able to function and the protesters no longer threatening to seize vital installations, however, it isn't clear how much pressure Mr. Khan's effort now poses on Mr. Sharif.
The government has allowed Mr. Khan "to fume and get exhausted," said Rasul Bakhsh Rais, director-general of the Institute of Strategic Studies, an Islamabad-based think tank. "How many times can you make a similar speech?"