Senate Foreign Relations Committee Chairman Sen. Bob Corker (R-Tenn.) is releasing a new Iran sanctions bill this week. (AP Photo/Andrew Harnik, File)

After months of negotiations, a small group led by Senate Foreign Relations Committee Chairman Bob Corker is introducing a new bill to impose sanctions on Iran, as Republicans continue to warn that last year’s nuclear deal with Iran was a dangerous mistake by the Obama administration.

But, so far, only two Democrats, both of whom opposed the Iran deal, are backing the measure.

The legislation seeks to step up mandatory sanctions against individuals and entities involved with Iran’s ballistic missile program, the Iranian Revolutionary Guard Corps, and cyber-threats and espionage efforts. It also would renew thorugh 2026 the expiring Iran Sanctions Act, or ISA, which outlines trade, energy, defense and banking sector sanctions over Iran’s nuclear and missile activities. In addition, the proposal would prohibit Iran’s financial institutions from engaging in dollar-based financial transactions with banks in third-party countries.

But Corker’s usual negotiating partner, committee ranking member Ben Cardin (D-Md.), is not on board with the compromise and is not expected to sign on anytime soon.

Corker said he began speaking with other members a few months ago after he and Cardin came to an impasse over waiver language. The chairman’s bill would prohibit the president from waiving any sanctions in order to enter into any new agreements with Tehran – a provision, Corker said, that is meant to make sure Congress has to approve any future deals with Iran before they can go forward.

“We wanted to ensure that no president could waive sanctions and implement an international agreement without congressional approval,” Corker said in a telephone interview Wednesday, pointing out that 98 senators voted last year to insist on a chance to review the Iran deal. “Most Democrats agree that a president should not be able to do that.”

But most Democrats have not signed on to the legislation yet, even though several oppose the nuclear deal with Tehran. Instead of Cardin, Corker teamed up with Sens. Bob Menendez (D-N.J.) and Joe Manchin (D-W.Va.), as well as Florida Republican Marco Rubio, all of whom opposed the Iran deal last summer, to introduce the bill.

Corker is hopeful that more Democrats will sign on over the summer. While Senate Majority Leader Mitch McConnell (R-Ky.) is being kept in the loop, Corker is only soliciting more co-sponsors in bipartisan pairs and hopes to build more support by September when the Senate returns from its seven week summer recess.

But building bipartisan support for the politically divisive issue will be difficult, particularly during an election season.

Menendez said he approached Corker three or four months ago with draft legislation he wrote after being dissatisfied with the answers he was getting from members of the administration during various rounds of testimony about the Iran deal.

“The administration generally has the position that they’re against everything,” Menendez said in a telephone interview Wednesday, pointing out that officials deflected even questions about renewing the ISA, which is fairly popular in Congress. “They have said no to everything; they wish that Congress would just go away.”

Like Corker, Menendez also rejected the notion that Democrats could legitimately pull away from the bill over the issue of waivers, arguing that there is “flexibility for the administration” in the sanctions regime, particularly when it comes to making case-by-case exceptions for national security and humanitarian reasons.

“That would be a false reason,” Menendez said. “If you don’t want to do something about broadening our efforts against Iranian aggression in other areas, fine, but you can’t use the waivers as a reason.”

Corker said he and his partners were “meticulous” about ensuring “that we are in no way involving any language that would touch the JCPOA,” a formal acronym for the Iran deal. “If we were to touch it in any way, the administration would say that we were undermining the nuclear deal, so this is in no way touches that – everything it deals with is outside.”

Cardin said Wednesday that Republicans rejected his attempts to include language to strengthen enforcement of the nuclear agreement, calling it an “area of contention.” He said he is still in discussions with GOP leaders about how to advance that provision.

Cardin also believes that the administration would be just as pleased if Congress did nothing on the subject of sanctions.

“The administration obviously recognizes that this issue could get out of control in the Congress, so they are not necessarily promoting any particular legislative strategy at this point,” Cardin told reporters Wednesday. “They’ll be very pleased if Congress does nothing.”

Cardin is not an advocate of Congress doing nothing. He stressed that “the way to proceed is to get Democrats and Republicans working together,” suggesting that the only way to do that this Congress might be to simply pass an unadorned renewal of the Iran Sanctions Act, which expires at the end of the year.

“That’s a pretty clear statement by Congress, unambiguous, and it will receive near-unanimous support,” Cardin said.

But neither chamber is pursuing any Iran measures that are that simple.

In the House, lawmakers will vote this week on a set of measures to step up sanctions against Iran over its ballistic missile program, human rights violations and support for terrorism. It also would prevent Iran from engaging in dollar-based transactions offshore and block the administration from striking any more deals to purchase heavy water from Iran.

Corker’s bill does not touch the heavy water issue, which came up in the Senate in the context of a budget bill earlier this year.

Last year, in the wake of failed attempts to defeat the Iran deal, McConnell said that he did not want to bring up any more Iran-related legislation that couldn’t get the support of at least 67 senators – the number necessary to kill the deal in the Senate.

Corker admits that it might be difficult to build Democratic support during an election season where the parties are deeply split over the legacy of the Iran agreement.

Presumptive Democratic nominee Hillary Clinton backed the deal, while presumptive GOP nominee Donald Trump has threatened to tear it up. Corker, who has advised Trump on foreign policy and was briefly being vetted as a vice president pick, said he had not discussed his plans to file an Iran sanctions bill with either candidate.

Corker also refused to speculate on a back-up plan if he is not able to build enough support for his proposal.

“I don’t want to say what we’ll do if this doesn’t happen,” Corker said.

But Menendez doesn’t think the election calendar matters. If politics make the road ahead for this legislation too complicated now, he said, Congress can still pass a simple reauthorization of the ISA down the line, likely with “a strong bipartisan vote.”

“There’s a lame duck session, where the politics don’t have to be a part of it,” Menendez said. And if that doesn’t work, bill sponsors can simply use the next few months “to build a foundation” for a more concerted effort at passing expanded Iran sanctions next year.