Former Sen. David Perdue (R-GA), whose defeat in a January runoff election handed the Senate majority to Democrats, is mounting a comeback bid—and his target is his former ally, Gov. Brian Kemp.

Perdue will run against Kemp in the Republican primary for Georgia governor next year, according to the Atlanta Journal Constitution. His move—which was teased for weeks—sets up what could be a historically brutal intraparty struggle.

Kemp’s team is hitting hard early, saying that Perdue is only running to “soothe his own bruised ego” after his loss at the hands of Sen. Jon Ossoff (D-GA).

The Perdue-Kemp battle is the next chapter in a dramatic Georgia GOP civil war that has been largely fueled by former President Donald Trump. Trump has not forgiven Kemp for refusing to overturn President Joe Biden’s 2020 win in Georgia; the Journal Constitution reports he is “assured” of winning the former president’s endorsement.

The winner is expected to face Democrat Stacey Abrams, who made her own campaign official last week, and will be one of the party’s most formidable candidates in 2022.