The state Office of Elections has tentatively set May 22 for a special election to fill out the remainder of U.S. Rep. Neil Abercrombie's term in Congress.

The date for the special election was included in an invitation to bid for vendors interested in providing voting equipment.

Abercrombie, D-Hawai'i, is resigning Sunday to campaign full time in the Democratic primary for governor.

Former U.S. Rep. Ed Case, state Senate President Colleen Hanabusa and Honolulu Councilman Charles Djou have said they would run in the special election.

The victor in the winner-take-all vote will serve the remaining months of Abercrombie's term, which ends in January.

The three candidates also have said they plan to run in the September primary and November general election to replace Abercrombie in Congress.

Scott Nago, the state's chief elections officer, said he would likely issue a proclamation in March calling the special election, after the bids are reviewed.

The vote will cost about $1 million. The elections office is asking Gov. Linda Lingle's administration to find the money by shuffling funds, releasing budgeted elections cash, seeking new appropriations and spending Help America Vote Act savings.