WASHINGTON — Allies of Rep. Alexandria Ocasio-Cortez, D-N.Y., and the other members of the so-called squad are expecting the progressive lawmakers to face potential primary challenges next year from more establishment-leaning forces, so they're working to shore them up politically now.

The labor union-backed Working Families Party, which missed their chance to endorse Ocasio-Cortez during her primary last year, is now offering an unusually early endorsement for the New York Democratic congresswoman and the three other members of "the squad," pledging to back them in intra-party fights or try to dissuade challengers before they materialize.

"They’re facing the combined institutional backlash of the right wing and corporate concerns within the Democratic Party. We think it’s very, very important that they be flanked," Maurice Mitchell, the party's new national director told NBC News. "When the resistance wins, the empire always finds a way of striking back, so we want to be prepared."

Left-wing groups are expected to circle the wagons around the lawmakers, four black and brown freshmen congresswomen who have sparred with Speaker Nancy Pelosi on one hand and become a target of President Donald Trump on the other, after he told them to "go back" to where they came from, even though three were born in the United States and all are U.S. citizens.

The four — Ocasio-Cortez, Minnesota Rep. Ilhan Omar, Michigan Rep. Rashida Tlaib and Massachusetts Rep. Ayanna Pressley — represent heavily Democratic districts where they won by either ousting longtime incumbents or emerging from crowded primaries, meaning that their toughest electoral opposition would likely come from within their own party.

It’s highly unusual for freshmen members of Congress to immediately lose renomination — but Ocasio-Cortez, Tlaib and Omar are highly unusual freshmen members of Congress.

Ocasio-Cortez defeated a local Democratic Party leader, former Rep. Joe Crowley, in a primary last year. Crowley's replacement, Rep. Greg Meeks, has also clashed with Ocasio-Cortez and suggested he’s looking for someone to run against her. “Primaries go two ways," Meeks told the New York Daily News when asked about Ocasio-Cortez.

Omar has made herself particularly controversial with statements some view as anti-Semitic, leading some local Democratic leaders and Jewish groups to look for alternatives, though there are no obvious would-be challengers waiting in the wings.

Meanwhile, many observers expect Detroit City Council President Brenda Jones to consider a rematch against Tlaib, given her own contentious comments on Israel, which also have some local Jewish groups urging change. Tlaib only narrowly beat Jones.

“I’m thrilled to be endorsed by the Working Families Party and am eager to continue fighting alongside them,” Tlaib said in a statement. “With policies like 'Medicare for All' and the Green New Deal, we need folks in the streets and up and down the ballot fighting to make them a reality.”

Pressley is seen as safer, since she was always more established in her district, having served for years on the Boston City Council and working inside the party.

The New York-based WFP works both within and outside the Democratic Party to help elect progressives and has seen recent success especially in down-ballot races in heavily Democratic places like New York, Chicago and Denver, where they tend to challenge local political establishments.

"This endorsement represents us putting our full institutional weight behind them," Mitchell said. "We want to signal to our partners and other folks in the field that this is the time to align around these members."