Rep. Pramila Jayapal (D-Wash.) announced Sunday that she has decided to endorse Sen. Bernie Sanders for president, adding to the list of notable progressive Democrats backing the Vermont senator.

Jayapal, who co-chairs the Congressional Progressive Caucus, said she chose to endorse Sanders because the senator “has a clarity on policy prescriptions that goes right to the heart of what working people need,” according to The Washington Post, which first reported news of the endorsement.

Jayapal will also be named the national health policy chair and the Washington State chair for the Sanders campaign, she told The Post. Jayapal, like Sanders, has been an outspoken advocate for “Medicare for All,” and was one of the first House Democrats to support the proposal.

Jayapal is expected to speak at a Sanders rally in Des Moines, Iowa, on Monday.

“Bernie has the bold passion, authenticity & clarity that working people across this country desperately need,” Jayapal tweeted. “We are building the progressive movement that will bring justice & opportunity & transform out country.”

The endorsement expands Sanders’ public support from progressive lawmakers. Rep. Mark Pocan (D-Wis.), the other co-chair of the CPC, endorsed the senator just days earlier.

Warren has formed a strong friendship with Jayapal in recent years, and the pair recently co-authored a letter to officials demanding to know what U.S. Immigration and Customs Enforcement and the Federal Bureau of Prisons are doing to prevent corruption and stop conflicts of interests in the private prison and detention industries.

Jayapal’s endorsement deals a blow to Warren, whose competition with Sanders for progressive endorsements appears to be growing as the two work to move past a conflict that dominated headlines over the past week.

Warren on Saturday received the endorsement of Janet Petersen, the Iowa state Senate’s Democratic leader. Both candidates’ endorsements in recent days could give them a surge ahead of the Feb. 3 Iowa Caucuses.