The United Auto Workers union is petitioning the National Labor Relations Board to hold an election at a Kentucky battery plant run by a Ford Motor joint venture, the union said in a release Wednesday.

The Kentucky autoworkers, who want to join the United Auto Workers, filed for a union election Tuesday, a key development in the union’s campaign to organize Southern auto-factories and EV battery facilities.

A supermajority of workers at BlueOval SK filed a petition with the National Labor Relations Board for a vote to form their union with the UAW.