Republican presidential contenders are unhappy with President Barack Obama's nuclear deal with Iran and vow to rescind the agreement, some on their first day in office.
But it may not be that easy.
If Iran lives up to its obligations, a new president could face big obstacles in turning that campaign promise into US policy. Among them: resistance from longtime American allies, an unravelling of the carefully crafted international sanctions, and damage to US standing with the rest of the world, according to foreign policy experts.
"The president does not have infinite ability to get other countries to go along with them," said Jon Alterman, director of the Middle East program at the Center for Strategic and International Studies. "One of the consequences is the United States would be increasingly isolated at a time when Iran is increasingly integrated with the rest of the world."
Both Obama and Republicans know firsthand the difficulties of dismantling major policies, a task that only gets harder the longer a policy has been in place.
After more than six years in office, Obama has failed to achieve his promise to shutter the Guantanamo Bay prison, despite signing an executive order authorising its closure on his first day in office. And more than five years after Obama's health care overhaul became law, Republicans have been unable to find a legal or legislative means for repealing the sweeping measure.
While some elements of the nuclear accord don't go into effect immediately, the centerpiece of the agreement is expected to be implemented quickly. If Iran curbs its nuclear program as promised, it will receive billions of dollars in relief from international sanctions.
To Republican presidential candidates, rolling back that quid pro quo would be a top priority if they were to win the White House.
Wisconsin Gov Scott Walker says he would "terminate the bad deal with Iran on day one" and work to persuade allies to reinstate economic sanctions lifted under the deal. Former Texas Gov Rick Perry concurred, saying one of his first actions in office would be to "invalidate the president's Iran agreement."
Jeb Bush, the former Florida governor, said that while he would consult with allies about the deal on his first day in office, he was inclined to "move toward the abrogation of it." Florida Sen Marco Rubio told The Associated Press he would withdraw from a deal even if allies objected.
The next president has no legal obligation to implement the nuclear agreement, which is a political document, not a binding treaty.
But if there's no sign Iran is cheating, it's unlikely the European allies, who spent nearly two years negotiating alongside the US, would be compelled to walk away and reinstate sanctions. And it's nearly impossible to imagine Russia and China, which partnered with the US, Britain, France and Germany in the talks, following a Republican president's lead.
