Caption:WASHINGTON, DC - MARCH 25: U.S. President Barack Obama speaks during an event marking the 5th anniversay of the Affordable Care Act March 25, 2015 at the South Court Auditorium of Eisenhower Executive Office Building in Washington, DC. President Obama spoke on the benefits of the legislation. (Photo by Alex Wong/Getty Images)
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Caption:WASHINGTON, DC - MARCH 25: U.S. President Barack Obama speaks during an event marking the 5th anniversay of the Affordable Care Act March 25, 2015 at the South Court Auditorium of Eisenhower Executive Office Building in Washington, DC. President Obama spoke on the benefits of the legislation. (Photo by Alex Wong/Getty Images)
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(CNN) —  

President Barack Obama on Thursday effectively placed his diplomatic legacy largely in the hands of Iranian revolutionary clerics who’ve waged a proxy war against the U.S. for three decades.

With a framework deal to halt Tehran’s nuclear program, Obama moved closer to the kind of staggering diplomatic breakthrough with the Islamic Republic that would have been unthinkable just a few years ago.

If the political agreement reached in Switzerland turns into a genuine pact honored by both sides, Obama will be entitled to a place in history as the leader who defused an intensely bitter estrangement with Iran.

READ: What’s in the Iran nuclear deal? 6 key points

But he also took personal ownership of a fraught negotiating process full of false starts and deep divisions, one that hinges on the sides’ ability to hammer out a host of devilish details by a June 30 final deadline in the face of vocal opposition from domestic and international critics.

If the deal falls apart, it will be hard to refute charges by critics that Obama’s insistence on negotiating directly with U.S. enemies – a tactic at the heart of his political philosophy – is deeply naive and futile.

The risks of Obama’s choice, and the challenge of resolving tough issues to get to a final agreement by July, were clear within minutes of news breaking that a deal was reached in Lausanne.

Obama quickly appeared in the White House Rose Garden, not for the victory lap that presidents often take in this picturesque spot, but to launch an impassioned defense of the contentious deal.

Obama’s sales pitch

His sales pitch was concise: There is no other better way to prevent Iran from moving covertly to build a nuclear weapon.

“When you hear the inevitable critics of the deal sound off, ask them a simple question: Do you really think that this verifiable deal, if fully implemented, backed by the world’s major powers, is