FILE - In this Oct. 19, 2010 file photo, Rep. Mazie Hirono, D-Hawaii participates in Meet the Candidates Forum at Maunawili Elementary School in Kailua. It&#39;s a once-in-a-generation occurrence: a competitive U.S. Senate race in Hawaii. And that&#39;s exactly what may be shaping up as two Democrats, Rep. Mazie Hirono and former Rep. Ed Case, square off in a primary Saturday. They&#39;re seeking the chance to take on former two-term Hawaii Gov. Linda Lingle in November. No matter which Democrat wins Saturday&#39;s primary, they&#39;ll face a tough fight from Lingle. The outcome could help determine the balance of power in Washington; Republicans need to gain four seats to take back control of the Senate. (AP Photo/Rebecca Breyer, File)