It's crunch time for architects of the carefully crafted, bipartisan bill to provide Congress a major oversight role in the potential deal to limit Iran's nuclear program.
GOP Sen. Bob Corker and Democratic Sen. Ben Cardin, the top members of the Senate Foreign Relations Committee, are working to keep poison pills at bay that could jeopardize Democratic support and the White House's reluctant pledge to sign the bill.
The bill has created unusual alliances: Neither Republican nor Democratic leaders want to see the current, fragile agreement disrupted. GOP senators eyeing runs for president are eager to demonstrate their support for Israel and antipathy towards Iran—even if their proposed amendments could destroy the bill's bipartisan backing. And the White House doesn't want the current bill to become more onerous, but it also never wanted this measure to move in the first place.
Corker, in carefully chosen words to reporters in the Capitol Monday evening, said his goal in this week's floor fight is to "maintain an appropriate balance so that we can have a very strong vote."
"I think there are enough members that understand there has to a balance maintained," he said.
The bill sailed through the panel 19-0 earlier this month, but several senators who wanted a more aggressive measure kept their powder dry, while lawmakers who aren't on that panel will now have chances to press for amendments of their own.
Sen. Marco Rubio, who is seeking the GOP White House nod, did not offer his amendment in committee to require that Iran recognize Israel's right to exist as part of the deal, while Sen. Ron Johnson did not press ahead with his plan to require that the deal be treated as a formal treaty.
Other amendments, if offered and successful—such as requiring certification that Iran is not supporting terrorism against Americans—would also jeopardize White House support.
Sen. Ted Cruz, another White House hopeful, has filed an amendment to require that Congress affirmatively approve the lifting of sanctions, whereas the current bill could only block that if Congress votes for disapproval.
Other GOP lawmakers are lining up to offer amendments, too. Sen. Roy Blunt said Monday he has an amendment package including a measure to make any U.S.-Iran deal contingent upon the "unconditional release" of the three Americans currently imprisoned in Iran: pastor Saeed Abedini, former Marine Amir Hekmati, and Washington Post reporter Jason Rezaian.
However, it was not clear Monday evening which amendments would actually be offered and come up for a vote during debate on the bill, which Corker said he hoped could be completed Thursday night.
Democratic Sen. Tim Kaine, who has been among the main Senate negotiators on the compromise bill, said he's optimistic.
"I think there's a real good understanding of those who supported it in committee and others who are not on the committee that we have got to keep it as nonpartisan as we can," Kaine told reporters in the Capitol.
He expressed confidence that Majority Leader Mitch McConnell, who has vowed an open amendment process, would not be a roadblock.
"I am not getting any sense that he is fomenting poison pills or trying to take the bill in any different direction than it is right now," Kaine said. "I am not getting any sense of that from my colleagues and others. So that is positive."
While Cardin and Corker say there could be some changes to the bill on the floor, they clearly don't want any major rewrites of the carefully crafted measure.
"I think the amendment process worked well in the committee, and we would hope that a similar commitment would be made by the rest of the Senate to respect the work of the committee, work with us, see whether we can deal with some of these amendments in a way that is not inconsistent with the bill," Cardin told reporters.
The White House, in the face of strong bipartisan support, agreed to support the bill this month after changes including removal of the terrorism certification provision and a shortening of the congressional review period.
But the White House has made very clear that President Obama's willingness to sign could evaporate if the bill hands Congress power to demand tougher conditions on the hoped-for agreement to limit Iran's nuclear program in exchange for sanctions relief. White House spokesman Josh Earnest has previously said that if there is an attempt "to undermine that compromise," then Obama "would absolutely veto that bill."