In the quiet of the August congressional recess, debate over the Iran nuclear deal is picking up online.

Virtually no social media platform has gone unused as groups lobbying on the deal launch digital campaigns to sway undecided lawmakers. Twitter, Facebook, YouTube and even Snapchat are seen as vital tools for mobilizing constituents to push their senators toward or away from the agreement.

“That is sort of where the main thrust of our engagement is coming from,” said Mark McNulty of the Republican Jewish Coalition, which opposes the deal, referring to Twitter and Facebook. “We’re targeting lists of Democrats and trying to get their constituents to put pressure on them.” McNulty declined to say how much the group is spending.

The campaigns are a reminder that micro-targeting is not merely a tool to shape elections. Thanks to data mining, interest groups can tailor their appeals to voters in an effort to convince lawmakers about any of the policy debates facing Congress — from Medicare to highways to foreign policy.

The nuclear deal between Iran and six nations led by the United States is putting those online methods to the test. Congress is out of town until September, complicating the logistics of lobbying members in person. And with just a few weeks until the House and Senate are expected to vote on resolutions disapproving the deal, advocates for and against it don’t have much time.

Citizens for a Nuclear Free Iran, an advocacy group launched by AIPAC this summer, is a big player among those paying to advertise online against the deal. Spokesman Patrick Dorton declined to state how much the group is spending, but said it is focused on reaching voters via Twitter and Facebook.

“There is growing public opposition to this weak ‎deal that is evidenced not only in polls but also in social media,” Dorton emailed.

Groups like Citizens are also using TV ads to get out their message.

Spending against the nuclear deal is expected to reach tens of millions of dollars in total, dwarfing the amount spent to support it. Secure America Now, another group that opposes the agreement, unveiled a new Snapchat ad on Wednesday targeting undecided Sen. Ben Cardin (D-Md.), ranking member of the Senate Foreign Relations Committee.

The ad is the first time Snapchat technology — specifically the platform’s “filter” feature” — has been used to lobby a specific lawmaker on a piece of legislation.

On the other side of the debate, has a six-figure budget for search ads on Facebook, Twitter and Google that support the deal.

Paid advertisements are not the only online ploy competing for voters’ attention. The Israel Project, which opposes the agreement, is working to create viral content that will take off on its own.

“We’ve been distributing  a lot of our social media resources through,” said Omri Ceren, managing director at The Israel Project. Ceren said the group’s Iran-related Facebook posts have reached more than 18 million people.

Anti-nuclear group Global Zero, meanwhile, enlisted celebrities for a YouTube video released July 28 in support of the deal. In the space of three minutes, stars including Jack Black, Morgan Freeman and Natasha Lyonne urge viewers to call on their lawmakers to vote for it. The video had been viewed 661,000 times on YouTube as of Thursday afternoon. (A spokesman said views totaled 2.49 million across the Internet.)

“The agreement currently on the table is the best way to ensure that Iran doesn’t build a f—ing bomb,” Freeman tells the camera.

According to the Post’s tally, there were 31 senators who supported the deal or were leaning toward it as of Thursday afternoon, while 57 were against or leaning against it. Twelve senators’ positions were unknown or unclear.

The latest announcements were good news for the Obama administration: Sens. Joe Donnelly (D-Ind.) and Claire McCaskill (D-Mo.) said Wednesday and Thursday that they would vote against a resolution opposing the agreement in September.

But the dwindling number of undecideds hasn’t stopped the Obama administration and members of Congress from keeping up the pressure on social media.

The White House’s official @TheIranDeal Twitter account remains active several times a day in support of the deal, though one of its posts — trying to play off the Straight Outta Compton meme — prompted a massive eye-roll on Twitter.

Republican lawmakers, on the other hand, are eager to highlight their ties to Israeli Prime Minister Benjamin Netanyahu. He opposes the deal.

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