The field for the upcoming City Council special election has begun to swell, with only two days before the filing deadline for candidates.

Former Councilwoman Ann Kobayashi filed her nomination papers yesterday, while former state Sen. Matt Matsunaga said he is seriously contemplating a run at the seat.

The Manoa-Kapahulu seat was left vacant when Councilman Duke Bainum died June 9 from complications of an aortic aneurysm. The winner of the race will serve through 2012.

Kobayashi held the seat from 2003 to last year. She chose to forgo a re-election bid in favor of an unsuccessful challenge against Mayor Mufi Hannemann.

Kobayashi, 72, a longtime Manoa resident, served on the state Senate before being elected to the council.

Matsunaga said last night he is "leaning toward running" for the seat. The Mo'ili'ili resident, 50, is the son of the late U.S. Sen. Spark Matsunaga.

A member of the state Senate from 1992 to 2002, the practicing business attorney said he is trying to determine if he can muster up the resources to make a viable run in a short period of time.

The deadline for candidates to file nomination papers is 4:30 p.m. tomorrow.

The offspring of two O'ahu community leaders also announced their plans to run.

They are Heidi Bornhorst, daughter of former Councilwoman Marilyn Bornhorst; and Nathaniel Kinney, whose father is Lynn Kinney, who heads the International Union of Painters and Allied Trades District Council 50.

Kinney, 29, is legal counsel for the painter's union and a Kapi'olani area resident. He filed yesterday. Bornhorst, 51, is a horticulturist who lives in Palolo. She intends to file today.

Those living in the district have until July 8 to become registered. About 48,000 ballots are expected to be mailed on or about July 17. Ballots for the all-mail election will need to be received by the clerk's office by 6 p.m. on Aug. 7. Results will be announced shortly thereafter.

Other candidates: