“There’s no way that Gavin Newsom should allow anyone other than a Black woman to fill the seat of Harris, who’s only the second Black woman in the history of the U.S. Senate,” Brown told POLITICO on Sunday. “There should be no contest.”

Brown’s campaign comes as some 150 of the state’s top female Democratic donors on Monday will publish full-page newspaper ads with an open letter urging Newsom to pick a woman of color, Vox reported Sunday.

The letter is officially authored by two donor groups, Electing Women Bay Area and the Los Angeles Women’s Collective. Signatories include Silicon Valley psychiatrist Karla Jurvetson, one of the country’s biggest Democratic donors; Gretchen Sisson, a sociologist and Democratic fundraiser; Susan Pritzker, a scion of the hotel family that has boosted Newsom’s political career over the years; and Dagmar Dolby, the billionaire philanthropist, Vox reported. The full list of donors will appear in ads in the San Francisco Chronicle and the Los Angeles Times.

Other leading advocacy groups like SheThePeople, which promotes women in politics, have called on Newsom to name a woman of color to the seat.