CHICAGO (CBS) — Making her first endorsement of a progressive challenger to an incumbent House Democrat, U.S. Rep. Alexandria Ocasio-Cortez is backing Marie Newman in her second bid to unseat eight-term Rep. Dan Lipinski, one of the more conservative Democrats on Capitol Hill.

Lipinski defeated Newman in the 2018 Democratic primary, but with a narrow lead of 42% to 40.15% — a total of 2,145 votes.

Ocasio-Cortez, who identifies as a Democratic socialist, is perhaps the most prominent freshman member of Congress, because of her support of progressive issues such as Medicare for all, the Green New Deal, and abolishing U.S. Immigration and Customs Enforcement.

“Marie Newman is a textbook example of one of the ways that we could be better as a party — to come from a deep blue seat and to be championing all the issues we need to be championing,” the rookie congresswoman told the New York Times.

In a statement, Lipinski said with Ocasio-Cortez’s endorsement, “It should now be clear to all that Marie Newman is running as an extremist.”

“I am a leader with commonsense plans to lower healthcare costs and fight climate change,” Lipinksi said in posts on Twitter and Facebook.

Ocasio-Cortez and Newman have said the anti-abortion Lipinski is too conservative for the 3rd District in Illinois, which includes parts of Chicago and the southwest suburbs.

“The fact that a deep blue seat is advocating for many parts of the Republican agenda is extremely problematic. We’re not talking about a swing state that is being forced to take tough votes,” Ocasio-Cortez told the New York Times.

While running against Lipinski in 2018, Newman slammed him for his votes against the Affordable Care Act, and the DREAM Act to provide a path to citizenship for some undocumented immigrants.

Newman thanked Ocasio-Cortez in posts on Twitter and Facebook on Tuesday.

“I’ve watched my community grow and progress and my Congressman fall behind. This is about electing someone who knows this district, who will fight for bold progressive policies that will make life more affordable for everyone,” Newman wrote in a tweet in response to Ocasio-Cortez’s endorsement.

Newman last week also won the backing of two Democratic presidential candidates – U.S. Senators Elizabeth Warren and Bernie Sanders.