As Lebanese prime minister Saad Hariri was in Washington to meet with President Obama this morning, Hezbollah and its allies withdrew from the Lebanese cabinet, setting the table for what many fear is an inevitable escalation of violence in the eastern Mediterranean. The Obama administration promises to support Hariri, but at some point the 39-year-old prime minister needs to know what Washington really wants—whether that’s to ensure stability in Lebanon, or to gamble on the possibility of handing Hezbollah a defeat. For Hariri, his life and maybe his country depend on him getting the right answers.

For the last several months, Hezbollah and its pro-Syrian allies have wanted Hariri to disown the findings of the United Nations’ Special Tribunal for Lebanon (STL), established to investigate the Feb 14, 2005 murder of Saad’s father, the former-Prime Minister Rafik Hariri. Reports and leaks from the STL suggest that Hezbollah members will be indicted for the murder, and Hassan Nasrallah, Hezbollah’s leader, has threatened violence in response. With the hope of avoiding confrontation, Saudi Arabia, Hariri’s patron, went into negotiations with Syria, and when they came to naught, Hezbollah went to Plan B, crashing Hariri’s cabinet.

The practical effect of the walkout is minimal: The government hasn’t been able to function anyway, frozen as it is thanks to the STL. Hezbollah may hope it can form its own cabinet, but right now the party doesn’t have the numbers. By walking out and threatening to go to the streets, Hezbollah seeks to terrify the Saudis and Hariri into granting them what the party’s Syrian ally could not win through talking—a rejection not only of the STL, but of all U.N. Security Council resolutions, starting with 1559, which demanded Hezbollah’s disarmament. In exchange for the international community granting impunity for political murder, and paving the way for a return to the status quo that existed before Syria’s 2005 withdrawal from Lebanon, Hezbollah promises not to set Beirut on fire, or not yet anyway.

Saad Hariri has shown remarkable courage by refusing to back down on his support for the tribunal, even as the Saudis have undermined him at every turn and French president Nicolas Sarkozy has played a less than helpful role. However, the fact is that even if Hariri wanted to scuttle the STL—and it was he who asked for it in the first place—it is not in his power to do so.  The tribunal is an international institution in pursuit of justice and is insensitive to political considerations—whether these are Saudi Arabia’s or Hezbollah’s. Nonetheless, Hezbollah is still capable of making plenty of trouble, even as it’s not clear what the party has to gain at this point through violence.

What Nasrallah fears most is that the indictments will show that a Shia organization is responsible for killing one of the region’s major Sunni leaders, Hariri. Hezbollah, the Party of God, is able to jump the Sunni-Shia divide thanks only to Hezbollah’s stalwart and successful resistance to Israel—but Hariri’s murder hanging over Hezbollah will make this tactic increasingly less viable. In other words, to try to protect the reputation of the resistance by going to the streets is destined to backfire, for it can only end with the Shiite militia killing yet more Sunnis.

There are plenty of variables, not least of which is what Iran wants to happen in Lebanon in the next few weeks. Obviously, the regime in Tehran will raise the stakes on Hariri, hoping to frighten the Saudis, but how far are the Iranians willing to push it? If outgoing head of the Mossad Meir Dagan is correct in his assessment, then the Iranians are four years away from a bomb, and it would be futile to spend their Lebanese asset so cheaply. And yet it’s also possible that if Hezbollah doesn’t act to protect itself now, the group might not be able to fill the same role of defense of Iran’s nuclear program that it has had for the last half decade.

And then there’s the Obama administration. Both the president and Secretary Clinton have told Hariri that they are 100 percent behind the tribunal. But what does that mean in practice? It’s easy to support the STL if Nasrallah intends to hand his indicted colleagues over to the Hague for trial; but it’s something else if Hezbollah tries to take over Beirut again as it did in May 2008—or, as they’ve threatened, renew an international campaign of terror like the 80s and 90s. Does Washington go all the way in support of its Lebanese allies, or when do we pull back, and let others, including those unfriendly to American interests, take the lead? The last thing we ought to be doing is getting the Lebanese to stick their necks out, if all this is leading to a replay of the Doha agreement that rewarded Hezbollah for its 2008 coup.

Presumably, these are the questions that keep Saad Hariri up at night, for no matter how much support he gets from Washington, the Lebanese, as Elliott Abrams wrote earlier today, “must take the lead… Those who wish Lebanon well must also hope that its political leaders and its populace show the considerable courage that this crisis demands of them.”