- Jeff Flake was seen by the Obama administration as a potential yes vote for nuclear proposal
- The Arizona senator has split from party before on some foreign policy matters
- Flake says he thinks Congress is too limited by the potential deal and wouldn't be able to impose sanctions
The White House and Democrats had hoped the Arizona Republican would support the potential deal.
Flake said in a statement released on his website that the Joint Comprehensive Plan of Action, as it is called, includes requirements he views as positives.
"But these benefits are outweighed by severe limitations the JCPOA places on Congress and future administrations in responding to Iran's non-nuclear behavior in the region," he said.
Flake, a member of the Senate Foreign Relations Committee, has broken with his party on foreign policy matters in the past. And he was the only Republican member of Congress to go to Africa with the President.
But the senator said he was concerned the White House wouldn't confront Iran on its interpretation of the proposal and therefore would be reluctant to challenge Tehran on is activities in the Mideast. He also believes the President's assurances that the deal doesn't affect Congress' ability to impose sanctions on Iran aren't confirmed by the text of the agreement.
"Hoping that Iran's nuclear ambitions might change after a 15-year sabbatical might be a bet worth making. Believing that Iran's regional behavior will change tomorrow -- while giving up tools to deter or modify such behavior -- is not," Flake said in his statement.
Flake's announcement comes as more Democrats late this week signaled they would back the agreement. On Thursday, Minnesota Sen. Al Franken, who is Jewish, voiced his support for the deal in a CNN op-ed. Montana Sen. Jon Tester also said he would support the deal on Thursday.
Although the loss of Flake likely means no Republicans will vote for the agreement, the White House is confident it can retain the necessary Democratic support to override a potential veto in the Senate.
So far, the GOP only has one solid Iran detractor among Democrats in the Senate, as New York Sen. Chuck Schumer expressed his opposition to the deal earlier this month. Senate Minority Leader Harry Reid said Wednesday he is still undecided.