Okinawa Gov. Takeshi Onaga's death last month at age 67 from pancreatic cancer came just over three months before the originally scheduled gubernatorial election and just days after he announced the prefectural government would take steps toward retracting permission for landfill work related to a new U.S. military base in Henoko, in northern Okinawa Island.

Onaga, who was elected in November 2014 by promising no new base would be built in the prefecture, had been ill for months. At the time of his death, it was uncertain if he would run again or designate a successor to carry on the legal battle with the central government over Henoko.

Official campaigning kicks off Thursday for the election that was rescheduled for Sept. 30.