Sen. Bernie Sanders (I-VT) endorsed Marie Newman in her bid to unseat Rep. Dan Lipinski (D-IL) Thursday morning, making him the latest big-name liberal to oppose the conservative Lipinski’s reelection.

“Marie Newman has made it clear that she will be a champion for working families in Illinois, which is why I am proud to support her campaign,” Sanders said in a statement released by Newman’s campaign, touting her support for universal Medicare, a $15 minimum wage, legal abortion, gay rights and undocumented immigrant rights. “I am proud to stand with Marie and look forward to continuing to fight alongside her on these and other critical issues once she’s elected to Congress.”

Sanders joins Sen. Kirsten Gillibrand (D-NY) and Reps. Jan Schakowsky (D-IL) and Luis Gutierrez (D-IL) in backing Newman, who is giving Lipinski his toughest challenge of his 14-year career and looks like she has a good shot at defeating him in their March 20 primary.

She’s also had huge help from an array of national liberal groups irate at Lipinski for bucking Democrats on key issues from Obamacare to immigration to abortion to gay rights in his decade-plus in Congress, even though he represents a safely Democratic district. NARAL Pro-Choice America, EMILY’s List, the SEIU, the Human Rights Campaign and MoveOn.org are all supporting Newman in the race.

Sanders won Lipinski’s district, which stretches from Chicago’s South Side into its southwestern suburbs, by 8 points in the 2016 Democratic primary. Lipinksi actually endorsed him afterwards and backed him at the Democratic National Convention, but their voting records have little in common except for a shared opposition to big trade deals.

A poll released by NARAL earlier this week found Lipinski clinging to a two-point lead over Newman in a race where he’d started out with a huge advantage.