Washington (CNN) Rep. Alexandria Ocasio-Cortez of New York on Tuesday threw her support behind a progressive primary challenger to Rep. Dan Lipinski of Illinois, a lawmaker who is considered to be one of the most conservative House Democrats.

Ocasio-Cortez called Marie Newman, who is challenging the congressman in 2020 after unsuccessfully challenging him in the 2018 midterm primary, "a grassroots fighter for working families" in a statement on Twitter.

"It's going to take a bigger, stronger Democratic Party - one that's returned to our FDR roots & fights for working people - to change our future in 2020," Ocasio-Cortez tweeted , adding, "We can't afford deep blue seats fighting against healthcare & equal rights. We need @Marie4Congress."

An endorsement from Ocasio-Cortez, who has quickly established herself as a progressive icon currently in her first term in Congress and has a massive following on social media, could give a boost to any candidate.

The New York Democrat also recently endorsed Democratic Sen. Ed Markey of Massachusetts in his 2020 re-election bid.

Lipinski is viewed by many liberal Democrats as out of step with his party. He voted against the Affordable Care Act, is one of the only congressional Democrats to identify as anti-abortion rights and did not endorse then-President Barack Obama's re-election bid in 2012.

Newman, in contrast, is running on a progressive platform, including supporting the Green New Deal and Medicare for All. She is backed by Justice Democrats, the progressive organization that supported Ocasio-Cortez when she ran a successful primary challenge to veteran House Democratic lawmaker Joe Crowley.

In a statement, Lipinski said, "Alexandria Ocasio-Cortez's endorsement of Marie Newman makes crystal clear that Ms. Newman is an extreme candidate who is completely out of step with the voters of Illinois' Third District who do not want to be represented by a fifth member of the 'Squad,'" a reference to Ocasio-Cortez as well as progressive Democratic Reps. Ilhan Omar of Minnesota, Rashida Tlaib of Michigan and Ayanna Pressley of Massachusetts.

"The Democratic Party - and our country - cannot afford an obstructionist 'Tea Party of the Left' when we need to focus on wining this next election and passing policies that will truly help working families and all who are struggling in America today," the congressman said.

Newman said in a statement of her own that she is "thrilled to receive the endorsement," saying that Ocasio-Cortez's "unwavering dedication to fighting for social, climate and economic justice is a true inspiration."

Alexandra Rojas, the executive director of Justice Democrats, said in a statement, "We are so proud that Marie Newman is the first Justice Democrat of this cycle to receive an endorsement from Congresswoman Alexandria Ocasio-Cortez."

The New York Times was first to report the endorsement.