Aside from the tens of millions of Jews and Arabs within missile reach of a future Iranian nuclear bomb, probably nobody on earth is more nervous about the new Iranian nuke deal than Democratic presidential aspirant Hillary Clinton.

The deal is built on an unexpected American concession. Until this month, the U.S. pressed other countries to support and enforce U.N. sanctions that called on Iran to stop enriching uranium. At Geneva, the U.S. abruptly changed policy—and undermined six U.N. Security Council resolutions in the process. 

And who was the first high American official to suggest the U.S. might accept an Iranian uranium enrichment program? None other than Clinton, all the way back in 2010. In an interview with BBC that year, the then-secretary of state said of Iran: “They can enrich uranium at some future date once they have demonstrated that they can do so in a responsible manner in accordance with international obligations.”

She made similar statements to other journalists that year, including Time’s Michael Crowley. It was obviously a carefully constructed trial balloon. Clinton tethered the balloon with conditions—“responsible manner,” “international obligations”—but there it was, fluttering beguilingly. “No, absolutely” had just been amended to “Yes, possibly.”

That amended formula made an impact on somebody. Iran’s new president, Hassan Rouhani, rose to power in Iranian politics as the country’s chief nuclear negotiator during the mid-2000s. In that job, he showed an acute ear for minute changes to the Western position. What Clinton offered in her BBC interview was anything but minute. It promised that Iran could gain a large measure of international acceptance without a total surrender of its nuclear capability. Three years later, that outcome is just what Rouhani has achieved.

Clinton ran for president in 2008 as a staunch defender of the national interest in a dangerous world, a tough-minded alternative to the dreamy Professor Obama. Asked in a July 2007 CNN debate whether he’d meet without preconditions with leaders of Iran, North Korea, and Cuba, Obama said, “I would.” Clinton scornfully replied, “I will not promise to meet with the leaders of these countries during my first year. I will promise a very vigorous diplomatic effort because I think it is not that you promise a meeting at that high a level before you know what the intentions are. I don’t want to be used for propaganda purposes.”

She was the candidate ready for the 3 a.m. phone call.  “Who do you want answering the phone?” (And let’s not forget the SNL parody of that pledge.)

If the Iran deal is seen to have compromised Israel’s security, or worse, Clinton will have some awkward explaining to do to important friends, supporters, and constituents.

If Clinton runs again in 2016, we’ll hear more on this subject. The leading Republican presidential candidates for 2016 have thin foreign-policy résumés. Clinton will want to use their inexperience against them, to argue that she alone knows how to keep the country safe in a perilous world. If it turns out that she miscalculated the peril from Iran, that strong claim will suddenly look wobbly.

Unlike her 2008 rival, Clinton was perceived as a trustworthy friend of Israel, an almost indispensable qualification in a senator from New York. If the Iran deal is seen to have compromised Israel’s security, or worse, she will have some awkward explaining to do to important friends, supporters, and constituents.

Obama and Secretary of State John Kerry have insisted that their agreement enhances Israel’s security. If they opened a secret channel to Iran, if they overrode Israeli concerns, if they dismissed the protests of Israel’s prime minister—well, they just knew better, that’s all. Some of their briefers even suggested that Prime Minister Benjamin Netanyahu’s concern about the Iranian nuclear program were not sincere, that he was really concerned not to stop an Iranian bomb, but to sabotage an emerging Iranian-U.S. friendship. (You can see the impress of this briefing in a November 20 Tom Friedman column, which restates this very argument.)

If the deal proves less than a resounding success, we may hear more of this line of argument: a denigration of critics of the deal as people not worth listening to. Awkwardly for Clinton, those critics may number more and more of the people whose support brought her as far as she has come.

We’ll also hear more of the backstory of how the Geneva deal was made: of the quiet relaxation of sanctions enforcement in the second half of 2013, as reported by Eli Lake and Josh Rogin in The Daily Beast earlier this month; and of the administration’s arguments in Congress against additional sanctions all this fall.

By then, of course, Clinton will be repositioning herself as a tough-on-Iran realist. That won’t be easy—not now, not anymore. Like the administration she served, like America’s allies in the Gulf, like the people of Israel, like the U.S. naval forces in the Persian Gulf, her candidacy will be on the firing line in case of failure. Like all of them, at this point, she’ll have to hope, “This had better work.”