Since mid-December, Pakistan has experienced political and economic volatility that is extraordinary even by Pakistani standards. The fragile political structure that began to be erected following the resumption of civilian government in 2008 is now shaking.

A key source of this unrest is Tahirul Qadri, a Toronto-based Muslim cleric who arrived in Lahore in early December. Ten days later, he addressed a mammoth public meeting at the city's Minar-e-Pakistan grounds, where, a year earlier, the cricketer-turned-politician Imran Khan had launched what he not very appropriately termed a political tsunami.

Qadri issued a 20-day ultimatum to the government in Islamabad to purge the political system of rampant corruption, reconstitute the Election Commission, and appoint a caretaker administration to oversee the upcoming vote. The caretakers, he said, should include technocrats, retired military officers, and judges — and could remain in office longer than the constitutionally permitted 90 days. Unless the government took these steps, he would lead a million-man march on the capital.