Sen. Barbara Mikulski's announcement Wednesday that she'll be the decisive 34th vote for President Barack Obama’s nuclear deal with Iran shifts the battle to the next major front: Whether the president will need to wield his veto pen in the first place.

The administration needed to stop opponents of the Iran deal from reaching a two-thirds majority to override a presidential veto of legislation to scuttle the deal. But the momentum to preserve the Iran accord moved dramatically in favor of Obama over the August recess — with Democrats from red states, in key leadership positions and of the Jewish faith coming out in favor of the nuclear accord. Now the question is whether the president can get to 41 votes, which would stop a disapproval resolution from getting through Congress.


Mikulski, a retiring senior Democrat, clinched it for Obama Wednesday, declaring in a lengthy statement that while no agreement is perfect – “especially one negotiated with the Iranian regime” – she has nevertheless decided to back to the deal.

“I have concluded that this Joint Comprehensive Plan of Action is the best option available to block Iran from having a nuclear bomb,” she said. “For these reasons, I will vote in favor of this deal.”

In addition to the crucial 34th vote in the Senate, House Minority Leader Nancy Pelosi of California has indicated that she’s confident there will be enough Democratic support in her chamber to sustain a veto of a resolution disapproving the Iran deal, should Obama issue one.

Her announcement secures a major foreign policy victory for Obama in his second term, despite vocal opposition from the GOP-led Congress and a small handful of Democrats worried that Tehran would still be able to build nuclear weapons.

After producing one version of an Iran review bill opposed by the Obama administration earlier this year, lawmakers crafted a review legislation later signed into law that would allow Congress an up-or-down vote on the nuclear accord.

But even with the handful of Democrats who oppose the deal, the Iran issue in Congress had sharply turned into a partisan one. No GOP lawmakers are expected to support the Iran deal in Congress, and a letter drafted by freshman Sen. Tom Cotton (R-Ark.) to Iranian leaders earlier this year dismissing any deal from Obama as “nothing more than an executive agreement” helped push the issue into a political one.

Opponents had been banking on the August recess – with boisterous town halls filled with constituents opposed to the Iran deal and an avalanche of ads -- to turn the tide against the agreement. But that strategy largely failed, with enough support in Congress now to protect the deal.

On Wednesday, Republicans continued to criticize the Iran deal, even as they acknowledged it will survive.

Senate Majority Leader Mitch McConnell (R-Ky.) said the Iran deal would be sustained “with the tepid, restricted and partisan support of one third of one House of Congress over American’ bipartisan opposition.”

“The fact that the administration has sought to reduce this important national security matter to a partisan contest raises even more serious questions about its durability and merits,” McConnell said.

Cory Fritz, a spokesman for Speaker John Boehner (R-Ohio), said: “Forcing a bad deal, over the objections of the American people and a majority in Congress, is no win for President Obama.”

“The White House may have convinced just enough Democrats to back an agreement that legitimizes Iran’s nuclear program, trusts the regime to self-inspect and offers amnesty to terrorists, but this deal is far from being implemented,” Fritz said.

The announcement from Mikulski came as her fellow Maryland Democrat, Sen. Ben Cardin, was speaking at a forum with students at the University of Maryland on the Iran deal. Cardin, the ranking member on the Foreign Relations Committee, is perhaps the most high-profile Senate Democrat who is still undecided on the Iran deal.

"I think it is clear that the agreement will go forward,” Cardin said, referring to Mikulski’s decision. “It doesn’t change my calculus."

Though Mikulski’s announcement relieves some of the pressure from Cardin and other undecided Senate Democrats from bearing the political pressure of being the deciding vote, the public push on other swing Democrats isn’t likely to let up.

Illustrating that pressure, the American Israel Public Affairs Committee will hold an event Thursday with former Sen. Joe Lieberman (I-Conn.) – a fervent opponent of the Iran deal – in Livingston, N.J., to urge Sen. Cory Booker (D-N.J.) to reject the deal in Congress.

Booker is still undecided on the Iran deal, as are several other key Democrats who could decide whether an Iran disapproval measure ends up advancing in the Senate – such as Richard Blumenthal of Connecticut, Gary Peters of Michigan and Michael Bennet of Colorado.

Only two Democrats in the Senate – Chuck Schumer of New York, a member of leadership, and Bob Menendez of New Jersey – have publicly declared they would reject the agreement that aims to curb Iran’s nuclear ambitions.

Obama’s Iran deal got an especially potent shot of momentum earlier this week when Sen. Chris Coons of Delaware, a Democrat who had voiced concerns with the agreement between six world powers and Iran, announced that he would support the accord.

But on Wednesday, Cardin – a lawmaker in a position of influence himself – dismissed the impact that one senator’s decision could have on another member.

“I’ve talked to every single, just about every member who has yet to make a decision and many, many, many who’ve made decisions,” Cardin told reporters on Wednesday. “And I haven’t found a single member who is waiting for anyone else to make a decision before they make a decision.”

Top Republicans have mulled forcing a vote on a resolution of approval – instead of a disapproval measure – on the Iran accord, essentially to have it fail and show the lack of support in Congress for the deal. So far, there has been no change in strategy, one GOP aide said Wednesday.