(Atta Kenare/AFP/Getty Images)

Iranian President Hassan Rouhani returned to Tehran this weekend to find his country's political establishment, after years of anti-Americanism, surprisingly supportive of his efforts to diplomatically engage the United States. His phone call with President Obama on Friday received lots of nods of support, possibly including from Supreme Leader Ali Khamenei, who sent a senior adviser to greet Rouhani's return flight. Even the head of the Republican Guards, hard-liner general Ali Akbar Jafari, showed some tepid support.

All of Rouhani's domestic support could, to be clear, disintegrate once the deal-making process goes from hypothetical to actual. Politicians in all countries have a way of retreating to the safety of rejectionism when it becomes clear that compromise requires concessions, and concessions can be painful. Still, in a sign of the remarkable mood change in Tehran and the sudden receptiveness toward diplomacy with the Great Satan, even former President Mahmoud Ahmadinejad seems to have expressed a bit of support.

Ahmadinejad, who for eight years championed hard-line "resistance" against the United States, reportedly told an Iranian outlet of Rouhani's phone call, "I don't know, perhaps it was the right thing to do." That's according to a translation by the University of North Carolina's Ali Reza Eshraghi.

No, it's not exactly a ringing endorsement, more of a shrug. Still, for Ahmadinejad to shrug at exactly the kind of thing you'd expect him to vehemently oppose seems interesting.

Ahmadinejad has been so sidelined since leaving office – perhaps even before leaving office – that he retains little actual influence. He is not in a position to exert much pressure on the Iranian political establishment. But his refusal to condemn Rouhani seems like a telling sign of the generally receptive mood in Tehran.