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 an electric vehicle battery campus in Hardin County has filed a petition with the National Labor Relations Board, asking for a union election. Employees of BlueOval SK have formally requested to vote on joining the United Auto Workers.

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.