Liberal protesters are eager to put members of Congress like Cruz on the defensive. (Photo by Win McNamee/Getty Images)

If 13 Senate Democrats and 44 House Democrats choose to oppose the nuclear agreement with Iran, it's as good as dead. The grassroots progressive group MoveOn is hammering that message home with its 8 million members, asking them to turn up at town halls or any other public events with their representatives.

"Like everything else that matters, that we work for, for change, for goodness, they've got money but we've got people," said Anna Galland, the executive director of MoveOn Civic Action, at a weekend panel at the progressive Netroots Nation conference. "We all need to make phone calls and write emails. We need to tweet. The alternative is war."

As the Post's Catherine Ho reported this week, progressive groups are raising money and trying out new tools for a campaign to save the Iran deal. In fundraising pitches -- J Street's has netted $2 million -- they portray themselves as Davids, taking on the Goliath of the Israel lobby. MoveOn is looking to spend "six figures" on a multi-platform ad campaign, and on hiring field organizers.

But MoveOn's most ambitious goal is to turn the long August recess of 2015 into the summer of peace. The inspiration comes -- just a little -- from the other side. In 2009, the last Democratic Congress was almost brought to heel at town halls, a combination of grassroots activism and top-level strategizing by groups like Americans for Prosperity. Tea Party activists packed the once-sleepy meetings of their local representatives. Some viral videos made some voters into celebrities; others made congressmen into former congressmen. (The 60-day countdown for congressional action on the deal takes the recess into consideration; had the deal been finished earlier, the countdown would have lasted 30 days.)

In an interview with The Washington Post, Galland said that the 2009 protests were motivated by "latent racism," while the MoveOn "mass mobilization" was a drive for peace. It would mark a return to MoveOn's heyday, in the run-up to the 2003 invasion of Iraq. During George W. Bush's presidency, what started as an organization asking Congress to "censure and move on" from the Bill Clinton scandals, became a potent anti-war force.

"It's been a long time since we've seen something like this," she said. "The mobilizations around the Iraq War were really the last visible effort."

There are two new, stiff challenges for any effort like this. One: In 2009, members of Congress discovered that they did not like being yelled at and seeing the videos show up on TV. Since then, "tele-townhalls" and smaller, invite-only forums have become more popular, and traditional town halls have started to decrease. According to Legistorm, the 535 voting members of Congress held a total of 588 public meetings in the 2014 recess -- down from an already paltry 792 the previous summer.

Problem two: MoveOn will have company. Galland framed its campaign as an answer an ongoing, expensive campaign by opponents of the deal. The American-Israeli Public Affairs Committee, or AIPAC, is supplementing one ad campaign that could cost as much as $20 million. But the bulk of AIPAC's effort is one-on-one lobbying, especially among safe Democratic members of Congress who balk at casting votes "against Israel." Last week, at its annual Washington conference, Christians United for Israel announced the creation of a political fund to move Congress against the deal.

"When the crowd heard that, the reaction just went over the top," said Gary Bauer, the long-time social conservative activist who serves as Washington director of the CUFI fund. "MoveOn should know we that have 2.2 million members and we’re planning on being wherever members of Congress are. We’re here, we’re going to be on the Hill, we’re going to be in their e-mail, we’re going to be at town hall meetings. It’s an extraordinarily important debate and we think we can bring a lot of oomph."

In her Netroots panel last week, Galland asked progressives to frame the debate in personal, moral terms. "These members need to ask themselves: What will my grandchildren or my great-grandchildren say about my vote? We need to tell them, this is about a new approach, a new way for peace."