The contest to replace U.S. Sen. Daniel K. Akaka is on, as former Hawaii congressman Ed Case became the first candidate to file nomination papers at the Office of Elections on Thursday.

For months, prominent Republicans and Democrats have announced plans to run for U.S. Senate in the 2012 election. U.S. Rep. Mazie Hirono hasn’t formalized her own bid for Senate yet, although she opened campaign headquarters in Honolulu last weekend.

Case and Hirono will face off in the Aug. 11 Democratic primary. The winner will move on to the general election, most likely against former Republican Gov. Linda Lingle.

Hawaii traditionally votes for Democratic candidates and hasn’t sent a Republican to the U.S. Senate in more than three decades. In 2002, however, Lingle became the first Republican elected to the governor’s seat in nearly 40 years by beating out Hirono.

With the balance of power in the Senate in question, the national GOP has incentive to try to help Lingle turn another seat.

Case held a news conference Thursday after signing his nomination forms.

"My campaign is about fixing Washington. My campaign is also about growing our economy, balancing our federal budget and confronting a great number of challenges, but it all starts with a better way of doing things inside of Washington," he said.

Setting up a contrast with Hirono, Case cast himself as a Washington outsider, although Hirono holds the seat he left in 2006 to run against Akaka for Senate.

Case used the opportunity to challenge Hirono to a public debate, saying that voters need to decide which candidate could perform best as a national leader.

Hirono’s spokeswman Betsy Lin said the congresswoman agrees that it’s important for the public to hear from candidates directly, which is why she holds frequent coffee talks and attends events across the state.

She also plans to debate Case, Lin said.

"Of course we will have debates, and Congresswoman Hirono has said all along that she looks forward to them," Lin said. "The Democratic primary will be held in August, we’ve been receiving and reviewing invitations, and will be announcing debate specifics soon."