Dan Drezner is skeptical that a Republican president would follow through on the threats to renege on a nuclear deal that Rubio, Walker, and Perry have made so far:

In the end, I think this is still the 2016 equivalent of renegotiating NAFTA, for a very simple reason. No Republican thinks that the Iranians will honor the terms of any deal. Therefore, any current debate will be overtaken by negative events come January 2017. Therefore, Rubio et al can say any damn thing they want about Iran now without any policy consequences.

So here’s the fun thought exercise to consider: If the Iran framework surmounts the obstacles to become an actual deal, and there is no evidence as of early 2017 that Iran has violated the terms of the deal, what would a GOP president do?

When it comes to foreign policy pledges, it is usually a safe bet that a candidate will at least try to fulfill the most prominent ones that he makes as a candidate. Indeed, a candidate sometimes ends up boxing himself in by making very firm commitments during the campaign that are then used to pressure him to act accordingly once in office. Instead of Obama’s lip service about renegotiating NAFTA, consider his repeated arguments as a candidate that the war in Afghanistan was the “good” war that needed the resources that had been mistakenly diverted to Iraq. Obama’s later decision to increase troop levels in Afghanistan was entirely in keeping with his previous campaign rhetoric, and the rhetoric made that decision harder to avoid once Obama was president. I submit that Republican candidates’ promises to scrap the nuclear deal are more like this than they are like Obama’s half-hearted pandering to Midwestern workers on trade almost twenty years after NAFTA was approved.

Because hostility to diplomacy with Iran is widely-shared among Republican candidates and members of Congress, a promise to renege on a deal with Iran is one that a Republican president would likely feel compelled to keep in order to keep the leading members of his own party satisfied. Unlike Obama’s line about renegotiating NAFTA (which his own chief economic adviser dismissed as pandering soon afterwards), rejecting the Iran deal is as close to a consensus view inside the GOP as one is likely to find. Republican Iran hawks are fiercely opposed to a nuclear deal and have been all along, and if nothing else the Cotton letter tells us that the senators that signed it, including Rubio, don’t expect any deal to survive an election of a Republican. If their presidential candidates say they intend to scrap it as soon as they have the chance, we should not doubt that they mean to do this. It’s always possible that one of these candidates could change his mind between now and 2017, but on such a high-profile and contentious issue on which almost all of the party’s candidates agree it seems very unlikely.

Apart from anything else, I assume that these candidates really do intend to scrap any deal reached with Iran because it is fairly common for a new president to define himself in opposition to his predecessor on at least a few significant foreign policy issues. Just as Bush began his tenure by ostentatiously engaging in unilateral actions that distinguished him from Clinton (e.g., withdrawing from the ABM Treaty, the rejection of Kyoto, etc.), and Obama made a point of reversing certain Bush-era policies, it is safe to assume that a Republican president would start 2017 with repudiations of some signature Obama policies. On most issues, there will probably be continuity from one administration to the next, but on a few prominent issues where there are real and substantive differences between the parties we should assume that a Republican hawk in the White House would do the things that Rubio, Walker, and Perry are threatening to do. I don’t think anyone doubts that a Republican president would cut ties with Cuba and revert back to the pre-2015 status quo. It is reasonable to assume that a Republican president would likewise reject the results of diplomatic engagement with Iran that he and most of the elected officials in his party have opposed from the beginning. Rubio and the other hard-line candidates want to define their campaigns by their loathing of diplomacy. We should take them at their word and judge them accordingly.