WASHINGTON – Last week in Vienna, Iran’s negotiators suggested that July 20 – a deadline self-imposed by world powers on their diplomatic effort to curb Iran’s nuclear program – might not be particularly important.The crisis is frozen, they argue, by the interim agreement that jump-started talks last fall. That deal, formally known as the Joint Plan of Action, allows for a six-month extension of talks should the United States, United Kingdom, France, Russia, China, Germany and Iran all agree to one.But while the Iranians say an extension would not be a “tragedy,” their American counterparts warn of political complications.Those difficulties became acute on Tuesday in the chambers of the US Senate.Sen. Bob Corker (R-Tennessee), ranking member of the Senate Foreign Relations Committee, proposed an amendment to the US-Israel Strategic Partnership Act last Thursday in a move that surprised his colleagues, just days before the scheduled vote on the bill. The amendment had no teeth: In the words of Corker himself on Tuesday, speaking to the committee, it was “the most watered-down amendment” on Iran and its nuclear program introduced in recent memory.That’s because its effects were intended to be political. The amendment would have triggered hearings on any deal that emerges from Vienna, and would have secured a vote in the Senate on whether or not the chamber approves of the agreement.In defense of his position, Corker told media website Al-Monitor on Tuesday that he had no interest in scuttling negotiations. “If it’s a good deal, I’m going to vote for it. I want a good outcome,” Corker said. “We haven’t been in the camp of wanting to add sanctions right now. We’ve been in the camp of wanting to find what a good deal is. So if we get a good deal, I’ll be glad to vote for it,” he said.But Corker’s move – his amendment led to the cancellation of a vote on the bill – suggests what might come next should negotiations fail to secure a deal this summer.Past July 20, all eyes in Washington will be on a different date: November 4, the midterm elections, in which Republicans are tipped to win back the Senate and take full control of Congress.If the US administration agrees to a deal, legislators will not have an opportunity to ratify it. But they will have an opportunity to gut it, for all its worth, by refusing to abide by its tenets. While US President Barack Obama may take executive action to lift certain penalties and enforcement mechanisms, Congress will ultimately be responsible for repealing the nuclear-related sanctions it has codified over the course of a decade. Already with Democrats in control of the Senate, Sen. Robert Menendez (D-New Jersey), Senate Foreign Relations Committee chairman, on Tuesday said that a vote for or against the repeal of sanctions will be “very significant” – Congress’ defining opportunity to either approve or reject the diplomatic outcome of Vienna.Should Menendez lose his chairmanship in November in a Republican takeover, it is difficult to imagine a GOP majority accepting detente with Iran as brokered by Obama’s State Department.The fusion of genuine concern and potential political gain, topped with fresh hopes of regaining the presidency, will be too intoxicating for Republican leadership. Asked whether the president would have the ability to unilaterally ease, lift or repeal sanctions through executive action, one senior administration official familiar with the negotiations told The Jerusalem Post that Congress has a "clear" role in the process moving forward."Building the sanctions regime was a major diplomatic achievement in which Congress played a critical role," the official said."It is too early to determine what a sanctions relief package would look like, since comprehensive negotiations are ongoing," the official added, "but, ultimately, comprehensive sanctions relief would clearly require a mix of executive and legislative action.”Thus, if the president agrees to an extension past July 20, he will face three months of congressmen and senators politicizing Iran policy in the lead-up to the midterm elections. Beyond that, he may face a Congress unable to uphold any prospective deal.The result of a rebuke from Congress would be historic – not often since President Woodrow Wilson proposed the League of Nations has an American foreign policy effort been accepted abroad and rejected at home. And it would ultimately result in the actualization of fears the White House has privately expressed: That the US, not Iran, will be considered intransigent on the international stage. Conflict with Iran will be more likely; who to blame, less clear.