Republicans are attacking Democrats backing the deal as soft on national defense.

The nuclear agreement with Iran is becoming an early campaign flash point in the battle for Senate control in 2016, fueling Republican attacks and creating divisions in contested Democratic primaries ahead of critical votes in Congress next month.

It�s a rare instance of foreign policy driving the debate in congressional races � in an off year, no less � and a potential preview of things to come if the Iran pact continues to generate heat into next year. Republicans are trying to portray Democrats backing the deal as weak on Israel and national defense. And some Democratic hopefuls are going after opponents for not taking a stand.

Nowhere has the issue been more prominent than in Pennsylvania, where GOP Sen. Pat Toomey is one of the most ardent critics of the agreement and former Democratic Rep. Joe Sestak, who served in the Navy for three decades, became a surprising early supporter for the deal. Meanwhile, Sestak�s primary opponent, Katie McGinty, a former chief of staff to the Pennsylvania governor who is a formidable contender for the Democratic nomination, hasn�t taken a position.

That�s created a rare moment of unity between Toomey and Sestak, who battled bitterly in a close 2010 election.

In an interview, the former two-term Democratic congressman said it�s inexcusable that McGinty hasn�t taken a stance and offered this advice: �Read the agreement.�
�Those who are running for an office that has anything to do with this [nuclear agreement] should have a position on this by now,� he said, saying candidates and politicians owe it to voters to make their positions known.

McGinty�s campaign scoffed at Sestak�s criticisms of McGinty, who was Pennsylvania Gov. Tom Wolf�s former chief of staff, but refused to directly engage with him.
�On this critical issue, Katie, like [Democratic] Sen. [Bob] Casey and others, is carefully assessing the impact of the proposed agreement on the nation�s security. ? While some Republicans are using this issue to score political points, Democrats need to remain focused on the facts and what is best for the country,� said McGinty campaign manager Mike Mikus.

But Republicans agree with Sestak. The National Republican Senatorial Committee has been calling out undecided Democratic candidates over the August recess even as a steady stream of Senate Democrats have come out in support of the deal.

�Obama�s nuclear deal with Iran is a defining national security issue. Any serious candidate running for office should have to answer if they support this nuclear deal that threatens our national security,� said NRSC spokeswoman Andrea Bozek.

On the Republicans� hit list are four current or potential Democratic candidates for Senate: McGinty, Rep. Tammy Duckworth in Illinois, Catherine Cortez Masto in Nevada and Gov. Maggie Hassan in New Hampshire, who is undecided on a Senate bid. On Monday, Republicans turned their focus toward Cortez Masto following news that retiring Senate Minority Leader Harry Reid (D-Nev.) is backing the Iran agreement.

National Democrats are providing Senate candidates with information about the deal but are not leaning on them to back the nuclear accord, sources said. And a spate of red-state Democratic senators up for reelection in 2018 supporting the deal suggest Democrats don�t fear retribution for backing the president.

Still, the Iran issue is putting Democratic candidates in awkward positions, particularly in the race for Obama�s old Illinois Senate seat. Mark Kirk (R-Ill.), perhaps the most vulnerable incumbent senator up for reelection next year, is staunchly against the agreement. On the Democratic side, Duckworth, an Iraq War veteran, is still undecided, her congressional office said. Duckworth�s primary opponent, former prosecutor and Chicago Urban League President Andrea Zopp, recently endorsed the deal.

On the other side of the Great Lakes, Ohio Republicans had been pelting the two Democratic candidates, former Ohio Gov. Ted Strickland and candidate P.G. Sittenfeld, for not taking a position. On Wednesday, both men came out in support of the deal, contrasting themselves with Sen. Rob Portman (R-Ohio), an outspoken critic of the Iran accord.

�Unlike Rob Portman, Democrats are taking a cutting-edge approach to figuring out where they stand by actually reading stuff before they take a position,� said Justin Barasky, a spokesman for the Democratic Senatorial Campaign Committee.

Portman campaign manager Corry Bliss said the senator �carefully studied� the deal before declaring it �dangerous.�

�Security will be a defining issue in this race,� Bliss added. On Monday, Portman launched an online ad campaign airing across Ohio saying Strickland �stands with President Obama and Hillary Clinton� on Iran.

Yet Democratic candidates aren�t in lockstep on the issue. Sen. Claire McCaskill of Missouri, who is not on the ballot next year, became one of a string of moderate Democrats to support the deal. But the Democratic Senate candidate whom McCaskill backs, Missouri Secretary of State Jason Kander, announced his opposition on the day the text of the pact was unveiled, lining up with his Republican opponent, Sen. Roy Blunt, on Iran.

�I expect our Democratic senators and candidates to have differing opinions on this issue because it�s a matter of conscience,� Barasky said. �Voters will hold Republicans accountable for irresponsibly advocating that Democrats say �yes or no� before they�ve even had a chance to review the deal.�

In Maryland, Rep. Donna Edwards became one of the earliest Democratic backers of the deal. A day after the agreement was announced, her campaign manager tweaked Democratic Rep. Chris Van Hollen for �holding his finger in the air,� but eventually he came out in favor of the deal. The two are competing in one of the most hotly contested Democratic Senate primaries in the country.

In several other Democratic primaries, candidates are waiting to see who blinks first. In California, Rep. Loretta Sanchez says she is �very reticent� to support the deal, while her Democratic Senate opponent, state Attorney General Kamala Harris, hasn�t weighed in.

And in Florida, rival Senate hopefuls Patrick Murphy and Alan Grayson, both House members, are warily eyeing each others� position on Iran in a state with more than a half-million Jewish citizens.

�The silence from Murphy and Grayson is deafening,� said Rep. Ron DeSantis (R-Fla.), a leading GOP candidate in that race.

On the House side, the two Democrats vying to challenge GOP Rep. Lee Zeldin � the only Jewish Republican in the House and a vocal opponent of the deal � have remained quiet.

Back in Pennsylvania, McGinty has been a candidate for less than three weeks but her campaign has given no indication she will announce a position on Iran before Congress votes in mid-September. Some Democrats predict she could get by without taking a firm stance. Coming out for it would give Toomey an avenue of attack, and opposing it would allow Sestak to criticize her for taking a stance at odds with liberal voters.

Sestak, who peppers his conversations with examples of his military experience, said if McGinty doesn�t take a position on the deal it will only feed into his narrative that the current crop of politicians aren�t ready to confront difficult national security decisions.

�We do not have senators today or candidates running today that can actually bring out the expertise and the knowledge,� Sestak said. �Politicians are unwilling to say: �Here�s where I stand.��

This article was written by Burgess Everett for Politico on Aug. 26, 2015. Burgess Everett is a congressional reporter for POLITICO. Previously he covered transportation policy and politics for POLITICO Pro and was a co-author of Morning Transportation.