Rep. Pramila Jayapal (D-Wash.), a co-chair of the Congressional Progressive Caucus and one of the most prominent women of color in Congress, is endorsing Sen. Bernie Sanders for president.

Her choice could bolster Sander's strength on the left and give him an advantage over his opponent Sen. Elizabeth Warren in the closing weeks before the first nominating contest in Iowa on February 3. Jayapal, the lead sponsor of the House "Medicare for All" bill, has been courted by both candidates for an endorsement.

"Bernie has the bold passion, authenticity & clarity that working people across this country desperately need," Jayapal wrote on Twitter. "We are building the progressive movement that will bring justice & opportunity & transform our country."

Jayapal will join Sanders for a rally in Des Moines, Iowa on Monday to unveil her endorsement.