Will Congress Overrule Obama’s Iran Nuclear Deal?

President Obama’s “historic” deal with Iran is getting panned on Capitol Hill. And not just by Republicans. Senator Chuck Schumer, the number three Senate Democrat, and Senator Bob Menendez, the chair of the Senate Foreign Relations Committee, are promising to work with their Republican colleagues on new sanctions legislation. Senate Majority Leader Harry Reid said last week he would schedule a sanctions vote when the Senate returns in two weeks from its Thanksgiving break.

Does this mean that Congress is going to take Iran policy out of Obama’s hands? Not quite. Any sanctions bill could be vetoed, something the president presumably would do to save his signature diplomatic initiative. The odds that sanctions proponents could override a veto aren’t good. Congress hasn’t overridden one in foreign policy since it imposed anti-apartheid sanctions on South Africa over Ronald Reagan’s objections back in 1986. In that respect, Obama is in a much stronger position than he was back in September when he sought to persuade Congress to authorize a military strike on Syria. Then the difficulties of passing legislation worked against him; now they work for him.

One reason Obama should be able to make a veto stick is party loyalty. Many congressional Democrats won’t see it in their interest to help Republicans rebuke him, and he only needs thirty-four senators to stand by him. Senator Reid has already begun to soften his commitment to holding a sanction vote. As Majority Leader he has considerable freedom to slow down bills and to keep them from being attached to must-pass legislation that would be politically hard for Obama to veto.

By the same token, however, daring Congress to override a veto is a high-risk strategy. That’s especially the case for a president whose public approval ratings are dropping and whose diplomatic initiative rests on the cooperation of a hostile and potentially unreliable foreign capital. Gloating from Iran or an unwelcome news leak about Iran’s nuclear progress could change the politics at home and send the president’s supporters rushing to the exits.

That’s why the most likely outcome of the battle brewing on Pennsylvania Avenue is not a duel at dawn but a negotiated settlement. The White House, with the help of its congressional allies, will look to shave off the most noxious provisions in the proposed legislation and fight for waiver provisions that maximize Obama’s discretion in implementing the law once it goes into effect. The result may complicate Obama’s diplomacy, but it likely won’t torpedo it.

However the battle plays out, the fight should strengthen Obama’s leverage with Iran in the near term. Congress is playing the “bad cop” to his “good cop.” If Iranian hardliners think their negotiators could have struck a better deal, the answer coming from Capitol Hill is a resounding no.