Politico reported Holder will campaign for Clinton in South Carolina ahead of the Democratic presidential debate Sunday in Charleston.
"I've seen her deal with the issues that will confront the next president firsthand, and she has bold plans to address police brutality, fight for common-sense reforms to our gun laws, get incomes rising and make college affordable," Holder said in a statement. "If we have a Republican president, they would tear down our progress on civil rights, healthcare and curbing gun violence. It can't and won't happen under Hillary, who has spent her life taking on the toughest fights."
Holder is not the only Cabinet secretary -- past or present -- to endorse Clinton. She's won endorsements from former Defense Secretary Leon Panetta and former Interior Secretary Ken Salazar, as well as current Housing and Urban Development Secretary Julián Castro, Transportation Secretary Anthony Foxx, Labor Secretary Tom Perez and Agriculture Secretary Tom Vilsack.