The administration's hard-won nuclear agreement with Iran faces hurdles once Congress begins its review. Democrats - although they largely hailed the deal as historic - are reserving judgment until they read the 100-page deal, while Republicans, who hold the majority in both the House and Senate, were skeptical after hearing the initial outline of the deal. House Speaker John Boehner, R-Ohio, suggested the House may fight to block it.
"The deal that we have out there, in my view, from what I know about it thus far, is unacceptable. It's going hand a dangerous regime billions of dollars in sanctions relief while paving the way for a nuclear Iran," Boehner told reporters at a press conference just hours after the deal was announced. "We are going to do everything we can to get to the details, and if in fact it is a bad a deal as I think it is at this moment, we will do everything we can to stop it."
The response was not much better from the Senate Majority Mitch McConnell, R-Kentucky. In a statement, McConnell said the deal "appears to further the flawed elements of April's interim agreement" and said the administration's approach was flawed.
"The Senate must now weigh why a nuclear agreement should result in reduced pressure on the world's leading state sponsor of terror," McConnell said.
Under the terms of the Iran Nuclear Agreement Review Act passed in May, Congress has 60 days to review the agreement before voting to approve, disapprove or do nothing about it (about half of the 60-day period will overlap with the month-long August recess). Lawmakers can't stop the U.S. from implementing the agreement entirely. But with a vote of disapproval, they can block the president from lifting some of the toughest sanctions against key sectors of Iran's economy that were implemented by Congress, which would almost certainly cause the deal to fall apart.
President Obama pledged Tuesday morning that he would veto any legislation that prevents successful implementation of the deal.
"We do not have to accept an inevitable spiral into conflict. We certainly shouldn't seek it," Mr. Obama said. "Precisely because the stakes are so high, this is not the time for politics or posturing. Tough talk from Washington does not solve problems."
With a nearly universal negative reaction from Republicans, the president's best chance of stopping Congress from scuttling the deal may be to build enough Democratic support to prevent the House and Senate from overriding his veto with a two-thirds vote.
Whether that is possible remains to be seen. One of the most positive statements came from House Minority Leader Nancy Pelosi, D-California, who praised the "tough, bold and clear-eyed leadership from President Obama."
"Aggressive restrictions and inspections offer the best long-term plan to stop Iran from building a nuclear weapon. Congress will closely review the details of this agreement," she said.
Senate Minority Leader Harry Reid, D-Nevada, also called the accord "historic" and said Congress should "review this agreement with the thoughtful, level-headed process an agreement of this magnitude deserves."
Sen. Chuck Schumer did not tip his hand in a statement about the deal, saying, "Supporting or opposing this agreement is not a decision to be made lightly, and I plan to carefully study the agreement before making an informed decision." The New York Democrat, who is in contention to become the Democratic leader when Reid retires, could help make or break Democratic support.
Maryland Sen. Ben Cardin, the top Democrat on the Senate Foreign Relations Committee, said his committee would be looking to ensure that the deal lasts for a long time and is verifiable, and that sanctions will be quick to snap back into place if Iran does not uphold its end of the agreement.
Cardin's Republican counterpart, Senate Foreign Relations Committee Chairman Bob Corker, could be a powerful Republican ally for the president if he backs the agreement. But in his initial reaction to the deal, Corker said that without having fully read the agreement, "I begin from a place of deep skepticism that the deal actually meets the goal of preventing Iran from obtaining a nuclear weapon."
The Senate has not yet set any hearings but the House Committee on Foreign Affairs jumped in Tuesday with a hearing that had been scheduled before the deal was announced. In his opening statement, Chairman Ed Royce, R-California, warned that the deal would leave the U.S. and its allies with "no effective measures to prevent Iran from initiating an accelerated nuclear program to produce the materials needed for a nuclear weapon. And Iran surely would be able to speed toward a nuclear weapon faster than an international sanctions regime could be reestablished." In a statement before the hearing, Royce said the deal would be a "tough sell" in Congress.
The top Democrat on the committee, Rep. Eliot Engel, D-New York, called the sanctions relief in the deal "deeply troubling" in a statement Tuesday morning.