20131118_me_09.mp3?orgId=1&topicId=1014&d=253&p=3&story=245847591&t=progseg&e=245063126&seg=9&ft=nprml&f=245847591

The White House has been fighting to prevent the disastrous rollout of the health care law from defining President Obama's second term. While that struggle continues, another story is unfolding this week that could shape this president's legacy.

Diplomats from the U.S. and other countries are going to meet for a second round of negotiations on Iran's nuclear program, and a breakthrough there could shape history's view of Obama.

Presidential second terms are often defined by foreign rather than domestic affairs, for better or worse. Ronald Reagan had his struggles in Central America and his breakthrough with Soviet leader Mikhael Gorbachev. President George W. Bush saw his occupation of Iraq become a bloodbath, and his troop surge help contain the violence there.

Historian Julian Zelizer of Princeton says one reason foreign policy often moves to the front burner in a second term is that domestic policy goals become much harder to reach.

"Even after re-election, presidents don't have that same kind of enthusiasm behind them in the next four years," Zelizer says. "Congress is often much more willing to cause problems for a president on the domestic front. They're just not as scared of him."

That's certainly true of President Obama. His gun bill fell to a filibuster in the Senate, immigration seems stuck in the House and pretty much everyone in Congress has panned the way his health care plan rolled out.

"I think foreign policy just isn't as much under the control of Congress, so there's always that opportunity even when things get very stifled for second-term presidents," he says.

Right now, the White House sees an opportunity with Iran. In a speech last week at the Middle East Institute, National Security Adviser Susan Rice said that for the first time in many years the U.S. is seeing "signs that Iran's leadership may be serious about a nuclear deal."

Even in this foreign arena, Congress could still block a deal. Many Republicans and some Democrats think a new round of sanctions would force Iran to offer more at the negotiating table.

"There is growing concern in Congress that the outlines of this agreement do not meet the standards needed to protect the United States and to protect U.S. allies," Republican Ed Royce, the chairman of the House Foreign Affairs Committee, said at a hearing last week.

President Obama sent his secretary of state to Congress to try to talk lawmakers out of passing new sanctions. The president said new sanctions would take the U.S. down a path that eventually leads to war. At a White House press conference, Obama urged people to give this potential deal a chance to work.

"If it turns out six months from now that they're not that serious ... we can dial those sanctions right back up," he said.

So a legacy-defining deal with Iran is far from a sure thing. Iran expert Cliff Kupchan of the Eurasia Group puts the chances slightly above 50 percent. He says if this does happen, it could profoundly shape history's view of Obama.

"A success in Iran would in effect create a trilogy: Afghanistan, Iraq [and] Iran," Kupchan says. "I think Iran would be central to it, though. In the first two cases he cleaned up someone else's mess, he ended other people's wars. Here, his sanctions and diplomacy would have led to his success."

It's a tantalizing hope for the White House and one that plays into a sunny West Wing narrative for the region that includes Syria giving up its chemical weapons and the Israeli-Palestinian peace process moving forward for the first time in years.

But another Iran expert, Patrick Clawson of the Washington Institute for Near East Policy, warns that even if the U.S. signs a deal with Iran and Congress gets on board, that deal may be less of a victory than the White House hopes.

"Which is to say that the two sides interpret the agreement differently," Clawson says. "The two sides have different expectations, that each side thinks the other side isn't fully living up to the agreement, that there's a bitter taste left in everybody's mouth about where this ends up, and there's a continuing crisis, sometimes low level [and] sometimes bubbling more to the surface."

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