The state Office of Elections says 684,481 people are registered for the Sept. 18 primary election. The number is higher than the 667,647 who registered for the 2008 primary, but lower than the 691,365 registered for the 2008 general election, when Hawaii’s Barack Obama won the presidency.

The deadline to register to vote in the primary election was Aug. 19. At the time, registrations were approaching record levels. However, since then, the Office of Elections has purged the voting rolls of those who have duplicate registrations and who have moved, said spokesman Rex Quidilla.

On Oahu, more than 77,000 people have requested absentee ballots so far, the City Clerk’s Office said yesterday.

Tomorrow is the deadline to request an absentee ballot for the primary. Absentee ballots must be received at the county clerk’s office by 6 p.m. on Election Day. Thursday is the last day to vote at the walk-in absentee voting sites.

Voter registration in Hawaii has been increasing steadily, but turnout has been dropping, especially in the primaries. In 2008, only 37 percent of registered voters here cast ballots, a record low.