Even as the White House celebrates a victory over Republican-led efforts to block the nuclear deal with Iran, concern persists over possible opposition from a different source: Iran's supreme leader, Ayatollah Ali Khamenei.
It has been assumed in Western capitals, and in Tehran, that the deal to curb the Iranian nuclear program in exchange for sanctions relief would never been have sealed on July 14 without the blessing of Iran's top official.
But in recent weeks, Khamenei has subtly distanced himself from the accord, sending signals that he is not happy with some aspects. Although there are competing explanations for why that may be, his moves and comments are nevertheless causing anxiety about the agreement's long-term durability.
The internationally negotiated pact has had to navigate a complex labyrinth of Iranian politics. Iranian leaders — especially Khamenei — do not want to appear too enthusiastic about an accord that has incurred the wrath of many Iranian hard-liners, who fear any hint of improved relations with Washington.
So while Khamenei continues to praise the Iranian diplomats who negotiated the deal, he has also given his approval for hard-liners to voice their unhappiness, including in the country's parliament.
"He's very clearly avoided putting his imprimatur on the deal," said Karim Sadjadpour, an Iran specialist at Carnegie Endowment for International Peace. "In three or four years we may look back and say that the leader's statements foreshadowed the fact that this was not something he was prepared to really commit to."
Rep. Adam Schiff (D-Burbank), the ranking minority member of the House Intelligence Committee and a supporter of the deal, said Khamenei "has left himself an exit."
The agreement between Iran and six world powers, including the United States, calls for the lifting of economic sanctions against Iran in exchange for curbs on its nuclear program. Iran has insisted that its nuclear efforts are strictly for peaceful purposes, such as generation of energy. Officials in the United States and elsewhere have long suspected that Tehran seeks nuclear weapons capability.
So far the deal has been most closely associated with Iran's president, Hassan Rouhani, a cleric who won the presidency in 2013 on a platform of breaking crippling economic sanctions and ending Iran's diplomatic isolation. Rouhani, who began the race as a dark-horse candidate, won the support of reformers and defeated several hard-line candidates.
But nearly all important decisions in Iran are made by Khamenei. Any role he took in forging and building consensus for the agreement has taken place very much outside public view.
One sign of Khamenei's views came late last month, when Hossein Shariatmadari, who is managing editor of the conservative Kayhan newspaper and often a mouthpiece for the supreme leader, wrote in an editorial that Khamenei is "well aware that the agreement could have disastrous consequences" and "is not in any way satisfied with the text."
But some analysts downplay Khamenei's actions, seeing them as largely driven by domestic political considerations as he attempts to placate hard-liners worried that the nuclear deal could open up new overtures to the West and even to Israel. Support for the Palestinians and opposition to the Israeli government are bedrock issues for Iranian leaders.
Conservatives in Iran, like many conservatives in the United States, view with deep suspicion the specter of a political rapprochement between Tehran and Washington after decades of adversarial relations. Khamenei, like President Obama, must sell the deal to a public that includes vast numbers of skeptics.
Khamenei has made it abundantly clear that the deal does not augur a broader opening to the West. This week, he issued a public declaration that the Islamic Republic "did not and will not hold talks with [the] U.S. on issues other than nuclear negotiations."
In the same speech, the supreme leader voiced the hope that "the Zionist regime" — Tehran's standard label for Israel — would not exist in 25 years.
In a speech this week, Khamenei even recalled the "Great Satan" sobriquet placed on the United States by Ayatollah Ruhollah Khomeini, the late leader of Iran's Islamic Revolution.
"Some people insist on disguising this Great Satan as the savior angel," the supreme leader said. However, he said, "the Iranian nation expelled this Satan; we must not allow that after we expelled it through the door, it could return and gain influence through the window."
Even so, Khamenei praised Iranian negotiators of the deal, who he said "did a good job."
Part of that balancing act stems from a desire to avoid alienating ordinary Iranians who hope the deal will bring a better economy and more contact with the world.
Sadjadpour, a supporter of the deal, said that Khamenei's willingness to compromise in the agreement may be rooted entirely in "economic expediency," and that after sanctions are lifted and the economy begins to improve, he will be ready to set it aside.
"That's a valid concern," said Sadjadpour.
And opponents of the agreement, such as Ray Takeyh, an Iran specialist at the Council on Foreign Relations, warn that it may not endure. Takeyh says Khamenei has been careful to make the agreement "a Rouhani deal and not a Khamenei deal.... He hasn't taken ownership of the deal, and that should concern everybody."
Obama administration officials say they can't predict what Iranian leaders' attitudes about the deal will be in the future. But they say they are confident that the agreement had Khamenei's support when it was signed. And they say that it was crafted to make sure Iran won't receive its benefits unless its leaders follow through on their commitments.
"They understood what the terms were when they agreed to the deal," said a State Department official, who was not authorized to discuss the agreement publicly. "They have to follow them."