Thousands of Hawai'i voters have already cast mail-in absentee ballots for the Nov. 7 election, and walk-in absentee polling places will open tomorrow on five islands.

Nearly 37 percent of all ballots cast for the Sept. 23 primary election were turned in before election day — the highest percentage in any Hawai'i election — and the trend is expected to be similar for the coming election.

Mail-in ballots account for most of the increase, as candidates aggressively seek votes early to ensure they register the maximum support, and voters opt for convenience.

Nearly 70,000 O'ahu voters have requested mail-in ballots, and about 5,000 had sent them in by late last week, said Honolulu City Clerk Denise DeCosta.

She said about 30,000 more on O'ahu are expected to vote early in person before walk-in absentee voting ends on Nov. 4, a Saturday.

That's the day when early voting is usually the busiest, so voters who want to avoid lines may wish to cast ballots earlier, DeCosta said.

Voters have until Oct. 31 to request a mail-in absentee ballot from their county clerk, but no advance notice is required to vote at the early walk-in sites. Voters must bring valid photo identification, such as a driver's license, to vote early at those sites.

More than 100 federal, state and county offices are at stake in the election. Republican Gov. Linda Lingle is defending her seat against long-shot Democratic challenger Randall Iwase.

Democratic former Lt. Gov. Mazie Hirono and Republican state Sen. Bob Hogue are facing off for the U.S. House seat that Rep. Ed Case is leaving after his unsuccessful Democratic primary campaign for the seat held by U.S. Sen. Daniel Akaka.

And Akaka will face Republican state Rep. Cynthia Thielen, who was named to replace winning GOP primary candidate Jerry Coffee after he bowed out of the race for health reasons.

Reach Johnny Brannon at jbrannon@honoluluadvertiser.com.