Former Democratic primary rival Pete Buttigieg has joined Joe Biden's presidential campaign.

Buttigieg, the former mayor of South Bend, Indiana, briefly led in the delegate count before Biden's come-from-behind victory in South Carolina. Buttigieg dropped out of the race in March.

According to Reuters, Biden named Buttigieg to his White House transition advisory board, together with former Deputy Attorney General Sally Yates and Susan Rice, national security adviser to former President Barack Obama.

Biden also added four new co-chairs to his White House transition team, including New Mexico Governor Michelle Lujan Grisham, former Obama economic adviser Jeffrey Zients, Louisiana Rep. Cedric Richmond, and Anita Dunn, a campaign adviser to Richmond.

“We are preparing for this transition amid the backdrop of a global health crisis and struggling economy,” said Ted Kaufman, who heads the Biden transition team. “This is a transition like no other, and the team being assembled will help Joe Biden meet the urgent challenges facing our country on day one.”

Buttigieg made history as the nation's first openly gay and married presidential candidate.