Voting began Sunday in the Okinawa gubernatorial election, with a controversial plan to relocate a key U.S. military base within the southern island prefecture high on the agenda.

Atsushi Sakima, a 54-year-old former Ginowan mayor backed by the ruling parties, and former opposition lawmaker Denny Tamaki, 58, are the major contenders for the seat left vacant by Takeshi Onaga, who died of pancreatic cancer in early August and was a staunch opponent of the relocation plan.

The result of the race could have an impact on the course of the plan to move U.S. Marine Corps Air Station Futenma from a crowded residential area of Ginowan to the less populated coastal district of Henoko in Nago.