Political uncertainty in Pakistan, a nuclear power, is more unnerving than it is in most other places. To the east, across the disputed region of Kashmir, lies India, Pakistan’s enemy since partition in 1947. To the west, across impenetrable mountain ranges, lies Afghanistan. Somewhere in these mountains, Osama bin Laden is believed to be hiding.

Before Sept. 11, 2001, worries about Pakistan centered mostly on its relationship with India. Since then, Pakistan’s western regions have commanded the world’s attention.

Within 24 hours of the terrorist attacks in New York and Washington, the Bush administration had Deputy Secretary of State Richard Armitage on the ground in Islamabad demanding Pakistan’s cooperation in the war the United States was about to unleash on the Taliban government of Afghanistan.

Pervez Musharraf, the military strongman who had seized power in 1999, later wrote that Mr. Armitage had said the United States would bomb his country “back to the Stone Age” unless it complied.

Mr. Armitage denied making such a threat, but history will record that within six months, President George W. Bush welcomed Mr. Musharraf to the White House and praised him as a ‘’leader of great courage and vision.” The United States began pouring the first of what would come to be $11 billion in military aid to Pakistan. Mr. Musharraf, still the head of Pakistan’s military, staged a bogus referendum and had himself ratified as Pakistan’s president.

On Monday — for reasons mostly, but not completely, unrelated to his close ties with Washington — Mr. Musharraf stepped down as Pakistan’s president. Had he not resigned, he most certainly would have been impeached. Control of Pakistan, a strategically located nation of immense complexity, is up for grabs.

For five years, Mr. Musharraf tried to split the difference between dictator and democrat. The army he controlled had forged alliances with fundamentalist Muslims who have great influence with the poor. Mr. Musharraf also reached out to Pakistan’s educated professional class with democratic reforms. New press freedoms encouraged the growth of newspapers, Internet sites and political talk shows.

But it’s difficult to be a popular leader when you’re rigging elections, especially when free expression is breaking out. It’s difficult to pretend to crack down on terrorists at the same time that religious fundamentalists are growing in power with at least the tacit cooperation of the army.

Mr. Musharraf showed some zeal in going after al-Qaida members, but much less enthusiasm for rooting out al-Qaida’s Taliban allies. His critics in Pakistan blamed him for cooperating with U.S. intelligence agencies and allowing the CIA and U.S. Special Forces to operate covertly. But U.S. forces complained that because of his domestic political problems, Mr. Musharraf’s support really wasn’t serious.

Mr. Bush stood by him in March 2007 when — trying to avoid free and open elections — Mr. Musharraf fired the chief justice of Pakistan’s Supreme Court, Iftikhar Muhammad Chaudhry, and again in December when former Prime Minister Benazir Bhutto was assassinated. Al-Qaida claimed responsibility for Ms. Bhutto’s death, but in combination with Mr. Chaudhry’s firing, it crystallized opposition to Mr. Musharraf. Mr. Musharraf declared a state of emergency late last year — just in time to get himself reelected president — but lost control of Parliament and was forced to give up his job as head of the military.

In the end, Mr. Musharraf was doomed because he was neither a particularly good strongman nor a particularly good democratic leader. Nor, despite billions in U.S. aid, was he a particularly good ally in the war on terrorism. The Taliban, which he helped the United States remove from Afghanistan, now operates in northwest Pakistan, where it provides protection for al-Qaida.

That he is gone suggests that democratic values, however raucous and disorganized, at least have a foothold in Pakistan. It also suggests how difficult it will be to keep that foothold.