Eli Broad, the billionaire philanthropist and a major advocate for U.S. charter schools, has come out against Education Secretary nominee Betsy DeVos in an open letter. The major defection comes as a few Republican senators announced they will not vote to confirm her, putting her nomination in serious jeopardy. “I believe she is unprepared and unqualified for the position,” Broad wrote in the letter addressed to Senate Majority Leader Mitch McConnell and Senate Minority Leader Charles Schumer. “Before Mrs. DeVos’s hearing, I had serious concerns about her support for unregulated charter schools and vouchers as well as the potential conflicts of interest she might bring to the job,” Broad added. DeVos has said she supports actions such as “school choice,” which would allow easier access to charter schools and direct public funds to private schools. Schumer has said DeVos would “decimate” public schools if confirmed.