Republican presidential candidate, Sen. Marco Rubio, R-Fla., mingles with potential voters at a campaign house party, Friday, April 17, 2015, in Manchester, N.H.

Republican presidential candidate, Sen. Marco Rubio, R-Fla., mingles with potential voters at a campaign house party, Friday, April 17, 2015, in Manchester, N.H. Elise Amendola/AP

The High Stakes Test for the Iran Deal — and the 2016 Contenders

The trio of Senate Republicans running for the presidency are unsheathing procedural weapons in a fight to burnish their national security credentials.

Mitch McConnell promised that when he became majority leader, the Senate would have an open amendment process. That's exactly what the chamber will get this week on a high-stakes Iran bill—a scary test for an already hard-fought deal between the administration, Republicans, and Democrats.

Senators from both parties—including the quartet eyeing presidential bids—will have the chance to push for tricky votes on Israel, terrorism, and American detainees abroad. Yet allowing that gauntlet is also the best way for McConnell to ensure that whenever the Senate takes a final vote to require congressional review of any nuclear agreement with Iran, the message will come through loud and clear: Whatever deal the White House strikes, Congress will be watching closely.

The Senate is expected to spend most of the week debating the Iran Nuclear Agreement Review Act, which received a unanimous vote in the Foreign Relations Committee earlier this month. It would require the administration to turn over the text of any finished agreement to Congress for a 30-day review. During that time, which could be extended, the White House would be prohibited from lifting sanctions.

If the final Iran nuclear agreement doesn't meet certain standards, these elected officials could make life very difficult for those who want them to sign off on it. The White House, which grudgingly agreed to accept the review process, is well aware of this.

But first, the Senate has to get there. And with the ability of any senator to offer any amendment for a vote, the deal could unravel.

"Any amendment, I worry about. There's nothing specific," said Sen. Ben Cardin, the ranking member on the Foreign Relations Committee.

So far, Democrats haven't offered any amendments, hoping to retain the deal as written. Sen. Robert Menendez, a key player in crafting the legislation, said he is afraid of "upsetting the balance" of the current legislation. He hopes senators will "stay as true as possible" to its current language.

Among the amendments already filed are several from Sen. Marco Rubio, who held his fire in committee on an amendment to require that Iran publicly recognize Israel as a Jewish state. That amendment, which Rubio has filed again on the floor with Sens. Mark Kirk and Pat Toomey, is among the "poison pills" that would kill the nuclear-review act.

Rubio and Sen. James Risch both have amendments to require that Iran release detained Americans, which will spark a conversation about how much the United States can trust a country not to build nuclear weapons when it imprisons Americans. Sen. John Barrasso has filed an amendment to require that Iran is not directly supporting terrorism.

Cardin and Foreign Relations Committee Chairman Bob Corker both have said that the conversations about terrorism and detainees are important issues to discuss, but they are not relevant to the nuclear talks. They say any broadening of the review process beyond specifics of a nuclear deal will weaken Congress's message.

Tell that to the folks running for president, who are skeptical that Iran will follow through on any of its promises and would like to adopt a much harder line. And they have voters to answer to. Sen. Rand Paul is still deciding whether he wants to offer any amendments, according to an aide. Rubio has filed his amendments, but if he follows his behavior in committee, he may stop before requiring a vote. Sen. Ted Cruz has filed one amendment to allow Congress to reinstate Iran sanctions under an expedited voting procedure. All in all, it could get messy.

Sen. John McCain says he's not worried, really. "Everybody knows what the parameters are of the deal," he told National Journal. "So let's see what happens. If you said there were no amendments allowed, then there would be a revolt. So you gotta roll the dice. I love rolling the dice."