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A new progressive Political Action Committee plans to recruit and fund primary opponents to Democratic members of Congress that it feels are not aggressive enough in fighting President Donald Trump.

WeWillReplaceYou.org was formed by a group of progressive activists with backgrounds in the Bernie Sanders campaign, the environmental movement, the Black Lives Matter movement, and the DREAMer movement of young undocumented immigrants.

It’s a project of #AllofUs, a new millennial progressive organization that has protested Democratic members of the Senate, urging them to draw a harder line against Trump's cabinet nominees and policy agenda.

While many liberals, including filmmaker Michael Moore, have issued nominal threats of left-wing challenges to Democratic lawmakers, WeWillReplaceYou.org appears to be the first organized effort to explicitly turn those threats into a reality. That will likely put it on a collision course with Democratic efforts to protect incumbents.

“Other groups are probably expecting to primary Democrats, but we think that it's important to make the threat clear now because so many Democrats are not fighting Trump forcefully enough and we need to communicate that we're serious,” Claire Sandberg, a former Sanders staffer and one of the group’s founders, told NBC News. “Our message to Democrats is pretty straightforward: Fight Trump or we'll find someone who will.”

The objective is not necessarily to replace Democratic incumbents, but to pressure them, Sandberg said, adding that the group is holding off on releasing any targets at the moment.

“We want to leave the door open for Democrats to improve and be stronger in their opposition to Trump,” said Sandberg. “We're only a few weeks into the Trump administration. Our goal is not primary every single Democratic member of Congress. It's to push Democrats who are there to do better.”

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WeWillReplaceYou.org will decide which Democrats to target based on where it can have an impact and through surveys of its members. There may be a handful of "litmus tests," the group suggested, such as voting against Trump’s Supreme Court nominee, Neil Gorsuch.

The group welcomes comparisons to the Tea Party, and it’s certain to attract familiar criticism from Democratic officials worried that primary challenges will undermine the party’s ability to retain seats.

Ten Democratic senators are up for reelection next year in states Trump won. Republicans now hold 52 seats and the Senate, and if they were to pick off 8 of those ten Democrats, the GOP would win a filibuster-proof 60-seat majority -- an outcome many Democrats would view as Armageddon.

Sandberg rejected the criticism that primary challenges to those Democrats would imperil the party's effort to hold those seats. Demoralizing the base with tepid opposition to Trump, Sandberg said, should be Democrats’ bigger fear.

“The same base that supports those primary challenges will propel them to victory in general elections,” she said.

But in places like West Virginia, where Democratic Sen. Joe Manchin is facing a tough reelection battle, Democrats will almost certainly need more than base voters alone to prevail. Trump won the state by over 40 percentage points.

Either way, primary challenges seem inevitable after an election loss that galvanized the left and nurtured doubts about party leadership.

“The 53 Senators, including Democrat Joe Manchin, who voted to put millions of jobs at risk by putting another Wall Street banker in charge of the Treasury Department shouldn’t expect to keep theirs,” Charles Chamberlain, the executive director of the liberal group Democracy for America said after Manchin joined Republicans in voting to confirm Treasury Secretary Steve Mnuchin Monday.

WeWillReplaceYou.org plans to raise money and organize volunteer efforts online, so the scale of its operations and the number of races it gets involved in will depend on how much support it receive.

But it hopes to operate on the cheap. The group plans to eschew expensive TV advertising in favor of some digital ads to support its main focus on distributed organizing, which leverages technology to generate phone calls, door knocks, and other volunteer efforts without the overhead of paid staff required by more traditional field programs.

As a hybrid PAC, the group can coordinate directly with campaigns in addition to fund independent expenditures.

In addition to Sandberg, who was the director of digital organizing on Sanders’ campaign, advisors to the new group include include Kenneth Pennington, Sanders’ former digital director, Rafael Navar, the national political director of the Communications Worker of America, May Boeve, the executive director of the environmental group 350 Action, Taj James, the executive director of Movement Strategy Center, former andra Flores-Quilty, the president of the United States Student Association and Carolina Canizales, a former United We Dream official.

All are working in their personal capacity, not on behalf of their groups.

Another advisor, Jessica Pierce, who once ran the NAACP’s field training program, said Democrats' current leadership has taken support from communities of color for granted.

“Even now our elected leaders are still failing us,” she said. “As someone who has run national election campaigns in every election cycle since 2006 , but who has also been a part of the momentum of the Movement for Black Lives -- I know that it is going to take all of, working strategically to make the change that people need. We must resist at every level-- from the streets to the Senate.”