No matter how what happens with the 2016 elections, the chances of the GOP blowing up the nuclear deal with Iran are extraordinarily slim.
First off, it’s not a treaty, so it doesn't need the approval of two-thirds of the Republican-controlled Senate. For a while this year, the Obama administration seemed to think they could cut Congress out of the process entirely, presumably using the executive waiver powers built into most of the relevant sanctions legislation; Obama initially threatened to veto Senator Bob Corker's bill to give Congress a vote on the deal.
The veto threat was withdrawn, and Corker's bill passed both houses of Congress with near-unanimous support (only the very hawkish Republican Tom Cotton voted no), because the process it establishes is heavily weighted toward approving the deal. If Congress does nothing (or if action gets bottled up in committee), the deal is approved by default. If a resolution of approval fails, it's a symbolic rebuke with no legal force. And if a resolution of disapproval passes, it needs veto-proof support to actually block U.S. participation in the deal.
That means the president would need to lose 13 Democrats in the Senate and 45 Democrats in the House (more if there are Republican defections in the other direction). That will, at the very least, be difficult.
Before the deal, some Democrats cited a letter put out by the Washington Institute for Near East Policy, signed by a bipartisan group that includes five former Obama advisers, that laid out guidelines for an acceptable deal.
The deal that’s been struck clearly doesn’t meet that bar; to take just one example, the letter demands that weapons inspectors "must have timely and effective access to any sites in Iran they need to visit in order to verify Iran’s compliance with the agreement." The deal makes it possible for Iran to delay inspections for up to 24 days. Nonetheless, the White House is circulating an argument that the deal not only meets but exceeds the letter’s benchmarks, and it’s quite possible, even probable, that the requisite number of lawmakers will buy their assertions.
And no matter what happens on Capitol Hill, the United Nations and the European Union will begin unwinding sanctions on Iran in short order; the UN will likely act even before Congress gets around to debating a disapproval resolution. And that makes things a lot trickier for the next president than some of the Republicans who want the job are letting on.
“As President,” Rick Perry said in a statement, “one of my first official acts will be to fully rescind this accord”—which, under a straightforward interpretation of “fully rescind,” is not actually possible.
Scott Walker at least said in his official campaign announcement on Monday that “we need to terminate the bad deal with Iran on day one, put in place crippling economic sanctions and convince our allies to do the same,” which at least includes a nod toward the fact that the sanctions are an international issue.
But with Iran open for business and European corporations eager to cash in, reviving the sanctions regime internationally almost certainly can’t be done in year one, much less on day one. If it’s possible at all, it would require a multi-year process of documenting Iranian violations of the deal to rebuild the consensus that has until now left Iran isolated. White House protestations to the contrary, the snapback provisions in the deal do little to change that.
To her credit, Carly Fiorina acknowledges this: “Even if Congress does vote this deal down, the rest of the world has moved on,” she notes. Fiorina advocates U.S. sanctions on Iran’s financial sector; that would have some bite, but without international cooperation it wouldn’t undo much of what Iran gets from the deal.
Other candidates are less candid: Ted Cruz echoes Walker’s "day one" phrasing, and Marco Rubio promises to “re-impose sanctions” but glosses over the limits on Washington’s ability to do so unilaterally.
Congress can pull the U.S. out of the deal; so can the next president. But at this point, Washington can do little to change the basic picture: Tehran is getting a massive windfall. Newly un-sanctioned Quds Force General Qasem Soleimani will be freer to spread mayhem across the region (if not the world). And, most likely, nothing short of regime change will stop the Islamic Republic from getting the bomb in the long run.