WASHINGTON — I sure hope that President Obama and his family enjoyed their week's vacation on Martha's Vineyard, because what he faces on his return to Washington is sheer hell.

Obama confronted a daunting situation when he took office back in January, with a sickening economic slide and the real threat of financial crisis. But he was buoyed then by the momentum of his historic election victory and the widespread hope that it stirred — even among those who had not voted for him.

He launched a series of ambitious initiatives and, while only the economic stimulus package came to quick fruition, there was a palpable sense of energy. By late summer, most of that good will has been dissipated, the voters are feeling impatient and irritable, and a sense of stalemate has returned to the capital. Meantime, at home and abroad, deadlines are piling up in a way that will test Obama's declining supply of political capital.

At least four large gambles are coming due. The first involves his signature domestic program, health care reform. The Senate Finance Committee has asked for an extension to work on its bipartisan compromise until Sept. 15, but the odds against its success have grown mightily.

I badly misjudged the public reaction to the angry August town meetings. Instead of provoking a pro-Obama backlash, as I had expected, the town halls, amplified on sometimes hostile cable channels and talk radio, spread disquiet about what the president has in mind. And Obama's patient, didactic responses have not quieted the reaction, let alone built fresh support for a vitally needed overhaul of our expensive, dysfunctional health system.

With congressional Democrats increasingly divided between moderates nervous about the cost of reform and liberals adamant that it not be compromised, it will take a major presidential push to get this effort back on track. But the early autumn will find Obama more than distracted by growing challenges in Iraq, Iran and Afghanistan.

In Iraq, the early stages of the stand-down of American troops have led to an upsurge of violence, casting serious doubt about the capacity of Iraqi forces to maintain the peace. And as Obama's promised troop withdrawal by September 2010 draws closer, the warring factions have become bolder. Prime Minister Nouri al-Maliki's government is beset by challenges, and the man in whom the United States has invested so much might not survive the coming parliamentary elections in power.

Iran is an even greater problem. Obama has given Tehran until Sept. 15 to respond to his offer of talks about their nuclear ambitions, but there is no sign that the hard-line government of Mahmoud Ahmadinejad will accommodate Obama or do anything more than seek delays while the centrifuges spin.

It looks likely that Obama will be forced to mount a major diplomatic offensive at the United Nations, particularly with Russia and China, to bring the Iranians into line. And there is no guarantee he can succeed.

Finally, there is Afghanistan. The election outcome is in doubt, and the U.S. hardly knows whether to hope that Hamid Karzai, hip deep in corruption, wins or not. The chairman of the Joint Chiefs of Staff has confirmed that the struggle with the Taliban and al-Qaida is going badly. The Afghan war, which once commanded broad support at home, is increasingly unpopular.

Meantime, an implacable and opportunistic Republican opposition savors the prospect of victories in off-year gubernatorial elections in New Jersey and Virginia.

As Washington mourns the death of Edward Kennedy, a rested but sobered president faces the toughest times he has yet encountered.

David Broder is a Washington Post columnist.