Pakistan’s rival political leaders seem determined to push their already unstable country over a cliff. Their increasingly out-of-control power struggle spilled out of the halls of government and the courtroom last week and onto the streets. The more time and energy they waste on selfish squabbling, the less they have to combat extremists who pose a mortal threat to their country.

We are especially alarmed to see President Asif Ali Zardari repeating the excesses of his predecessor, General Pervez Musharraf. Six months after taking office, Zardari’s government has banned Nawaz Sharif, a former prime minister, and his brother from holding office. It issued a two-week halt on rallies and threatened to charge Sharif with sedition. On Thursday, police in riot gear forcibly dispersed some of the thousands of Pakistanis marching from Karachi to Islamabad in support of an independent judiciary.

The US ambassador in Islamabad spoke with Sharif, and an envoy, Richard Holbrooke, had a video conference call with Zardari. They need to press Zardari to compromise on the dispute over Pakistan’s courts and to allow Sharif to run for office. If there is any hope for democracy in Pakistan, a robust opposition must be allowed to flourish and participate fully in the country’s political life.