“If you were to clock success in flight time hours and international meetings, he is clearly succeeding,” said Kathleen Hicks, who was deputy Defense undersecretary on global and regional defense policy and strategy in Obama’s first term and now is director of the International Security Program at the Center for Strategic and International Studies. She urged caution on the early judgments of any Iran deal.

“There are so many factors swirling around these talks—the politics in Washington, the politics in Tehran, the allies, Russia—that it will be hard, even if it wildly succeeds, to say the success is Kerry’s. Or, if it fails, to pin it on him.”

She singled out the relationship Kerry has forged with Zarif as one of the biggest pluses of the talks. “This isn’t about trust. It’s about establishing a working relationship,” she said, stressing the value of opening a channel to an adversary “to be able to discuss issues and prevent any kind of miscalculation.”

Pollack also noted a benefit of Kerry’s hard work that will pay off even if the talks collapse, stating that it will be important how the two sides are positioned if there is a failure.