During my travels in Turkey, Syria, and Egypt, I've been talking about this with Syrian rebels, both civilian and military, including an impressive female vice president of the new coalition. (More about her below.) For the new body to succeed, they all said, the Obama administration will have to take the lead in supporting it. And the president will have to focus far more intensely on Syria than he has in his first term.
Here's why this new group matters: Before last weekend, the main Syrian opposition group, the Syrian National Council, was unable to unify the rebels. Composed mainly of exiles, it didn't represent the Syrian resistance on the ground.
Much of the resistance consists of ordinary civilians trying to govern in areas from which the regime has retreated; it also includes many secular or moderate Muslim fighters. Because they have had no organized structure, these rebels have received little aid from the West. (U.S. assistance has been limited mainly to communications equipment and training courses.) On the other hand, rich Gulf Arabs have showered militant fighters with money and arms, boosting their numbers.
The new coalition could provide a channel for international aid to civilian councils in liberated areas. Already, the French government and six Arab Gulf states have recognized the body as Syria's legitimate authority. It has the potential to become an interim transitional government that can further sap the legitimacy of Bashar al-Assad's regime.
Equally important, if the coalition can organize a military command structure inside Syria, Britain and France may extend military aid, especially if it's used to defend civilians. The rebels need ground-to-air weapons to stop the regime from bombing towns and cities. This, in turn, would enable the creation of a de facto buffer zone along the Turkish border - with no need for NATO planes or troops.
The Obama administration and the Europeans have so far refused to supply ground-to-air weapons for fear they might fall into the hands of militants. But such weapons are already trickling into Syria, and if the war doesn't end soon, jihadis will surely obtain them.
The new rebel council is supposed to set up a centralized military command system so that small numbers of critical weapons can be delivered to vetted units and commanders. This could tip the military balance and end the current stalemate, which must happen before there can be a negotiated end to the Assad regime.
The new coalition is especially encouraging because of its president, Sheikh Ahmed Moaz al-Khatib, the former imam of the historic Umayyad Mosque in Damascus. He comes from a well-known family of Islamic scholars, has a degree in geophysics, and was imprisoned during the early phase of the uprising.
"Khatib is a central figure who has enormous legitimacy," said Joshua Landis, a noted American expert on Syria. The sheikh is a religious moderate who has called for political pluralism and opposed sectarian divisions. This sends a critical message to Assad's Alawite sect that its members have a future in Syria if he is ousted.
"It also undercuts the Muslim Brotherhood," Landis added, and counters the appeal of radical Islam.
So that's the good news.
We still don't know whether the council can demonstrate that it truly represents all the Syrian people. However, we do know the coalition won't get off the ground unless the United States and Europe show support by providing concrete resources, starting at a donors' conference in London on Friday. Rhetorical support alone will not suffice.
When I met one of the two vice presidents of the new coalition, Suhair Atassi - an attractive, secular woman from a noted Syrian political family, wearing jeans and a sleeveless top - she was adamant on this point. "We hope the United States and the Europeans will really get involved now," she said.
Over the past two years, the West has left it up to the Gulf Arabs to back Syrian rebels, Atassi complained, and they channeled their aid to "the wrong people." She meant the Islamists. With a credible Syrian transition body, she said, she hopes that will change.
Then she delivered a warning: "It will be much worse for Syria and the countries all around if this [coalition] doesn't work." That would create a vacuum, she said, that would be filled by jihadis.
She was absolutely correct.
Trudy Rubin can be reached at email@example.com.