As he basks in legacy-defining wins at home, the President's hopes of extending his hot streak rest on controversial gambits engaging U.S. enemies and reversing tenets that have underpinned American foreign policy for decades.
Even if they succeed, they will pay out only when he has left office. If they fail, by leaving a repressive communist regime in Havana miles from America's shore, or Iran with a nuclear weapon, they will tarnish his name in posterity.
Both initiatives are not just deeply important to the U.S. posture on the world stage, they are the ultimate test of an idea central to Obama's political DNA: that talking to U.S. adversaries instead of fighting them is a show of strength and not weakness.
And each also has the potential to elevate Obama's uneven record as a global statesman, a record that hasn't yet lived up to towering expectations challenged by a turbulent world resistant to U.S. power and a troublesome generation of foreign leaders.
"The world is much more complicated these days, and it is harder to get those clean victories in the sense that we had in the '90s in various peace agreements or victories in war," said Brian Katulis of the progressive Center for American Progress.
Critical stage for Iran and Cuba
Obama's quest for a nuclear deal with Iran and his opening to communist Cuba are both at a critical stage, and they are coming to a head just weeks after the main building blocks of his domestic legacy settled into place.
Supreme Court victories on health care and gay rights, rare bipartisan agreement on a crucial trade push, progress in battling unemployment and Obama's moving sermon on race combined to enliven the second term of his presidency.
But even if U.S. negotiators emerge in the coming days from nuclear talks in Vienna with a deal with Iran and the plan to open an embassy triggers reform in Havana, Obama is unlikely to enjoy the kind of quick political boost delivered by his recent domestic bonanza.
That's because both initiatives are not at all assured of success and remain deeply controversial in Washington, where distrust of the President's diplomacy is not limited to the his usual Republican critics.
Even Obama admits the risks. As he told The Atlantic in May: "Look, 20 years from now, I'm still going to be around, God willing. If Iran has a nuclear weapon, it's my name on this."
And while Obama argues that the best way to promote political change in Cuba is engagement, if Cuba doesn't respond to his overtures by improving its human rights and democratization record -- or the situation worsens -- his whole theory of talking with U.S. adversaries will be undermined, with serious consequences for his legacy.
His Iran and Cuba diplomacy is also symbolically vital because, although the administration has racked up some achievements, it cannot yet boast a major strategic victory abroad.
The Iran deal could make it into that category. The plan is to freeze Iran's nuclear program a year or so away from the point where it could produce a weapon. In return, world powers would begin to ease sanctions that have throttled Iran's economy.
If negotiators beat a deadline this week and produce a deal, Obama will argue that diplomacy has triumphed and alleviated the need for another U.S. strike in the Middle East, this time to thwart an Iranian bomb.
And last week, Obama declared that it was time to end a policy that had failed for half a century, when he announced plans to reopen diplomatic relations with Cuba.
GOP could derail policies
He has already removed some retractions on travel and trade, but the full economic and financial embargo can only be lifted by Congress, where suspicion of the island's leadership still runs deep.
Since most Republican presidential candidates oppose the move, the full fruition of Obama's Cuba initiative may rely on a Democrat winning the White House in 2016. And a GOP president could also look to unroll the Iran deal, which will not be legally binding.
U.S. presidents in their second terms often look for big victories abroad as their power at home wanes.
But Obama is an anomaly; his domestic legacy is in better shape than his global one.
"When we get to the end of the presidency, we will look back and the conclusion will be that he was considerably more successful domestically than he was internationally," said David Rothkopf, CEO and editor of the Foreign Policy Group, which has a respected journal and website. "Even if he improves his record, it is still going to be a mixed one at the best."
Many of the initiatives that flourished in Obama's first term -- the withdrawal from Iraq, targeting core al Qaeda leaders and resetting relations with Russia -- look less impressive in retrospect.
So the stakes for the Iran and Cuba endeavors are even higher. If Obama could add a proposed pan-Pacific trade deal that would enshrine his Asia pivot and secure agreements at a global warming conference in Paris, 2015 could end up his most successful foreign policy year yet.
Obama's backers argue that he has done quite well abroad, particularly considering the difficult situation he inherited from President George W. Bush.
They claim big wins in his recall of troops from Afghanistan and Iraq and a nuclear arms reduction deal with Moscow, and they maintain that he repaired U.S. alliances in Europe strained by the Iraq war while reinvigorating U.S. standing in East Asia.
Obama also hunted down Osama bin Laden and employed a ruthless drone campaign and expansive surveillance program that have helped prevent another large-scale terror attack on U.S. soil.
"When you measure it against the inheritance, the mess left behind ... the world's problems certainly haven't diminished, but I think we have seen some important progress," Katulis said.
World becomes less stable
Yet it is hard to argue that the world is a more stable place than when Obama took office. The extent to which he is personally to blame for that is one of the early questions shaping the 2016 presidential race.
Last week, New Jersey Gov. Chris Christie, for instance, accused Obama of showing "weakness and indecisiveness in the Oval Office" that had "led to weak leadership around the world, where our friends can no longer trust us and our adversaries no longer fear us."
Obama's critics often point to a pugnacious Russia, which has defied American warnings after biting off Crimea and waging a covert war in Ukraine, while Russian President Vladimir Putin has rekindled Cold War animosities in Europe.
Nuclear-armed North Korea only got more dangerous on Obama's watch.
Rising China is, meanwhile, increasingly provocative and nationalistic. It has challenged U.S. allies, made muscular maritime territorial claims and may have perpetrated a huge cyber hack on sensitive U.S. government servers.
In the perennially violent Middle East, Iraq has been partially consumed by ISIS, a vicious extremist group with American blood on its hands that the president once dismissed as a "JV" team. Critics say Obama opened the way for ISIS after withdrawing all U.S. troops from the country.
Syria is an even worse humanitarian disaster, where ISIS is only one problem. The al-Assad regime has continued chemical attacks on civilians despite Obama having declared that an American red line.
Libya is a failed state following U.S.-led regime change. America's relations with Israel are at their lowest ebb. Obama's anti-terror alliance in Yemen has crumbled. Iran has spread geopolitical tentacles throughout the Middle East, and U.S. allies such as Saudi Arabia despair of Obama's diplomacy.
A new generation of Islamic militants now threatens the West, which is now living in fear of homegrown, radicalized, lone wolf extremists. The State Department reports that worldwide terror attacks jumped by a third and fatalities soared by 81% last year.
ISIS on the offensive
Obama's campaign against ISIS, which includes air strikes in Syria and Iraq and tentative help for Kurdish and Syrian opposition rebels, seems incapable of reaching his goal of degrading and destroying the group.
"One of the reasons they are able to recruit so may individuals is it looks like they are taking on America and they are winning," Republican Rep. Martha McSally of Arizona said on CNN's "The Situation Room" this week.
For some, Obama's Middle East policy is one of deliberate disengagement.
"The less the U.S. has done, the more dangerous the region has become," said Vali Nasr, who worked in Obama's State Department during the first term, suggesting that Obama overlearned the lessons of neoconservative overreach under Bush.
"The U.S. went from having a huge Middle East policy to having a minimal Middle East policy," he said. "The pendulum has swung the opposite way toward deliberate avoidance of any kind of vision for the region."
To which Obama's closest aides, such as Ben Rhodes, a deputy national security adviser, answer: "Americans are not going to be able to impose order on the Middle East."
Speaking at the Aspen Ideas Festival, Rhodes warned that using force in the region needed to be carefully considered since it could draw the United States into military engagements that are difficult to escape.
"The President is measured and he takes a lot of criticism; but the fact is, you get the criticism and the day after you use military action, it shifts to, well, what's the exit strategy, what's the plan here?" he said.
Aides say that Obama, abroad as well as at home, is playing the long game.
But that's not how his critics see it. They accuse him of lacking strategic vision, pointing to his prolonged agonizing over Afghan and Syria policy and say he is short on diplomatic muscle, evidenced in rocky encounters with leaders such as Putin and China's President Xi Jinping.
Leaders test Obama
"These leaders test Obama on a regular basis and they have discovered that if they are tough, and they play by their own rules, and they ignore international public opinion, and they ignore statements of the White House's preferences for their behavior, that they can do whatever they want with impunity," said Rothkopf.
Some of the catchphrases most associated with the White House's approach to foreign policy haven't helped.
At various times, Obama has compared foreign policy to picking off singles and doubles and then hitting the odd home run. And he was criticized after it emerged he told close aides his approach was based on the mantra "don't do stupid s**t." A remark attributed to an unnamed official to the New Yorker that Washington was "leading from behind" on Libya has haunted the administration for years.
Which is part of the reason why success with Iran and Cuba looms so large.
It would reconcile Obama's vision for the conduct of international relations, and be the product of thought-out, diligent diplomacy that could yield the very global transformations that he seeks.
And in the eyes of the world, if not his critics back home, it could finally help justify the Nobel Peace Prize that even the president says he was prematurely awarded in 2009.