But only one politician can truly assure the commission’s independence and success: Hamid Karzai. He is a courageous man with whom I have met several times, although not on this last trip. He cannot seek re-election, and so he stands in a perfect position now to secure his place in Afghan history by insuring that future elections will be more fair and credible than past ones have been. The decisions Mr. Karzai makes now, including his appointments of electoral commissioners and his deference to the commission’s work, will be the last and truest test of his statesmanship. As a politician and a citizen, he will have every right to campaign for his preferred candidate. But as the country’s chief executive, he has a duty to act now to ensure a fair election whose results are broadly accepted. So he should consult with opposition figures on the naming of the next electoral commissioners, and appoint a commission that is widely perceived to be balanced and impartial. That would show an early and decisive commitment to a truly democratic election.

As for the United States, its current policy is, correctly, to insist on a fair electoral process without taking sides in the contest. But that goal must be pursued more urgently. The Afghans I spoke to felt strongly that the United States should already be pressing the government and the international community for a final plan for fair elections; it should also provide the necessary support to guarantee its execution.

The Afghans I spoke to acknowledged that strong American pressure might be denounced as interference with Afghanistan’s sovereign rights. But for the vast majority of Afghans, they argued, anything less than forceful, visible American leadership would be viewed as tacit United States support for an electoral process that gives unfair advantages to some ethnic groups or individuals. “Existential stakes trump niceties,” said one Afghan political activist, noting that the United States and its allies are currently responsible for the major part of Afghanistan’s security and economy.

The options facing Afghanistan and its allies are stark. Unless a credible election legitimizes a successor to Mr. Karzai, Afghanistan’s fragile political order will most likely implode, followed by the disintegration of its security forces, a renewal of harsh civil war and the resurgence of Taliban forces. These threats explain why both the Strategic Partnership Agreement signed by the Afghan and United States governments in May and the Mutual Accountability Framework agreed upon by Afghanistan and numerous donors in Tokyo in July made clear that future aid for Afghanistan will depend upon successful elections and improved democratic governance. Under those agreements, rigging the elections or failing to hold them would almost certainly lead to sharp reductions in foreign aid, which could in turn wreak havoc with Afghanistan’s economy and add to political instability and armed conflict.

A great deal of technical work will have to be done, in not much time, to correct serious problems with the voter registry and to assure both security and a level political playing field. Mostly, what Afghans need now is forceful leadership from their president to let them fairly choose his successor. Given Afghanistan’s history, such an achievement would be heroic. Mr. Karzai should be that hero.