The office of Sen. Rand Paul (R., Ky.) signaled on Friday afternoon that he would support a new bipartisan Iran sanctions measure currently under consideration in the Senate.
This leaves Sen. Jeff Flake (R., Ariz.) as the lone Republican who has publicly refused to take a stand on the bill.
A senior Paul staffer told the Washington Free Beacon that Paul is keeping "an open mind on the bill."
"Sen. Paul has not said he wouldn't support it in a vote," the Paul aide told the Free Beacon. "He has supported previous sanctions, and believes they have helped bring Iran to the [negotiating] table. "
"The timing of this vote is important, and since [Paul] can't determine when it will be brought up, he will for now keep an open mind on the bill," the source said.
The Iran sanctions bill – which would level tougher sanctions on Tehran if it refuses to comply with the parameters of a recently signed nuclear accord— has garnered the support of 59 senators, including 43 Republicans and 16 Democrats.
A senior Senate aide additionally confirmed to the Free Beacon a CNN report that a veto-proof threshold of 77 senators now support the sanctions measure.
Senate sources said there are signs that at least 34 Democrats will vote in favor of the bill when it finally comes up for a vote.
Paul and Flake remain the only Republicans who have avoided taking a firm stand.
Flake’s office would not respond to multiple requests for comment about his position.
Flake has a complicated history when it comes to the issue of Iran sanctions.
Before running for the Senate in 2011, Flake opposed Iran sanctions, leading to criticism from Democratic opponents.
Flake eventually changed his position and voted in favor of a 2011 sanctions resolution
"Limiting the Iranian regime’s access to the capital it needs to produce nuclear weapons is a necessary action to be taken," Flake said in a statement issued at the time. "Putting a choke hold on Iran’s financial resources could avert disaster for Israel and the rest of the Middle East."
Flake’s refusal to take a public stand on the latest round of sanctions has some Republicans wondering if he will once again flip his position on the issue.
"I think in the end, Jeff Flake does not want to be the only Republican who opposed holding a terrorist regime accountable during negotiations," one GOP congressional aide tracking the sanctions debate told the Free Beacon.
"Rand Paul's openness to this legislation demonstrates that the White House's outlandish warmongering rhetoric is not based in reality," added the source, referring to a Friday statement that accused sanctions supporters of promoting war.
"If certain members of Congress want the United States to take military action, they should be up front with the American public and say so," National Security Council (NSC) spokeswoman Bernadette Meehan told the Huffington Post. "Otherwise, it’s not clear why any member of Congress would support a bill that possibly closes the door on diplomacy and makes it more likely that the United States will have to choose between military options or allowing Iran’s nuclear program to proceed."
The Republican Jewish Coalition (RJC) took aim at both Flake and Paul in Friday statement.
"We are disappointed that two GOP Senators have thus far failed to join their colleagues as cosponsors and we hope they will yet agree to sign on," said RJC executive director Matt Brooks, who urged Senate Majority Leader Harry Reid (D., Nev.) to promptly bring the bill to a vote.
"In contrast to the Republicans, 16 of 55 (29 percent) Democrat senators have cosponsored the bill, which speaks volumes about the tensions within their caucus about the necessity of confronting a serious threat affecting the U.S. and our allies," Brooks added.
Following publication, a Flake spokesperson emailed the Free Beacon a statement attributed to the senator.
"Talks on implementation of the Nov. 24 agreement are ongoing, but time is running out," the statement said. "If Iran is simply using this as another stalling tactic, further congressional action will be warranted."