A progressive group allied with Rep. Alexandria Ocasio-Cortez announced on Friday that it would target Rep. Henry Cuellar of Texas for a primary challenge in 2020.

Cuellar is one of the most conservative Democrats in the House, despite representing a deep-blue district.

The Texan is the progressive left's first target in a controversial national effort to target incumbent Democrats in safe blue districts.

Justice Democrats, the progressive group that helped Rep. Alexandria Ocasio-Cortez win her insurgent primary bid, announced on Friday that it would recruit a 2020 primary challenger to Rep. Henry Cuellar, a conservative Democrat who represents a deep-blue South Texas district.

Progressives argue that Cuellar is the ideal Democrat to challenge — he's one of the most conservative Democrats in the House, his South Texas district is safely blue, and he's even allied himself with Republicans in recent years. Last year, Cuellar controversially fundraised for GOP Rep. John Carter, a fellow Texan, in his competitive race against the Democrat MJ Hegar.

The activists want to replicate the 2018 successes of Ocasio-Cortez and Rep. Ayanna Pressley, both of whom ousted popular longtime incumbents in their deeply Democratic districts. They've established a fund that will support a candidate they'll help recruit for the primary race.

"We're trying to build on our learnings and successes from AOC's primary victory against Joe Crowley, which was to start early on recruitment and campaigning," Waleed Shahid, Justice Democrats' communications director, told INSIDER, using Ocasio-Cortez's nickname. "We also want to show Democrats and progressives that we need a mission-driven caucus in Congress of people just like AOC who will take risks and fight back just like she does."

Cuellar has held his seat since 2005 — and hasn't faced a competitive primary in 12 years. He insists he maintains a strong hold on his seat.

"They came after me twice, and I beat 'em," Cuellar told The Washington Post last year. "LBJ used to say: What's the difference between a cannibal and a liberal Democrat? Cannibals don't eat their own."

Liberal critics point to Cuellar's conservative legislative record — he's voted with President Donald Trump 65% of the time — as reason enough to oust him. His district, which stretches from parts of San Antonio to the US-Mexico border, went for Hillary Clinton in 2016 by nearly 20 points.

Progressives have long been critical of Cuellar's work in Congress.

"Henry Cuellar is a f---ing disgrace, a vile misogynist, and a Trumpist," Sean McElwee, a progressive activist who founded Data for Progress, told INSIDER. "The sooner he is gone, the sooner the Democratic Party can embrace its progressive future."

They argue that Democratic leadership will have a hard time defending the lawmaker.

"Can Pelosi, Hoyer, and the Democratic Party leadership really defend that Cuellar is a real Democrat after receiving an A rating from the NRA and voting to defund sanctuary cities?" Shahid said, referring to House Speaker Nancy Pelosi and House Majority Leader Steny Hoyer.

An array of progressive activists and groups expressed support for the initiative on Friday.

"Cuellar had a 43 percent score from us on civil rights and civil liberties. Much room for improvement!" Faiz Shakir, the American Civil Liberties Union political director, tweeted, citing the organization's legislative scorecard.

Shahid said the group's next steps would involve building relationships with organizers and activists on the ground in Texas to begin the candidate-recruitment process.

But Justice Democrats have found little solidarity with their effort among members of Congress.

The push to move the party left has upset many Democrats who want the caucus to remain focused on their Republican opponents.

Even some of the House's most progressive lawmakers — including Rep. Ro Khanna, a California Democrat endorsed by the group and the only member of Congress to support Ocasio-Cortez's primary bid — have said they won't sign on to the effort.

"I believe that you should have competitive elections and that everyone in this country has a right to run, but personally I would like to see our focus on turning Texas blue, winning states in the Midwest, Michigan, Pennsylvania, Wisconsin, making sure we expand our majority," Khanna told INSIDER in an interview last month.

Ocasio-Cortez has also declined to publicly declare support for the effort to oust Cuellar.

"We're not active in their process," Ocasio-Cortez's press secretary, Corbin Trent, told The Post. "We're focused on getting up and going."

But on a November call with Justice Democrats and other activists, Ocasio-Cortez and some of her top aides encouraged fellow progressives to run against incumbents.

"We've got to primary folks," said Saikat Chakrabarti, the former executive director of Justice Democrats and now Ocasio-Cortez's chief of staff.