Honolulu Mayor Mufi Hannemann's decision to launch a gubernatorial exploratory committee almost certainly precludes any congressional campaign, according to a Hannemann supporter.

Hannemann had considered running for the open congressional seat being vacated by U.S. Rep. Neil Abercrombie, who is running for governor.

But Hannemann volunteer Elisa Yadao said the mayor, who is in the first year of his second four-year term, will not quickly decide if he is going to run for governor.

If he does decide to run, he will be helped by the more than $600,000 he has in his campaign treasury, left over from his last race for mayor.

Hannemann declined to speak about his possible plans yesterday, citing the death of Councilman Duke Bainum, just hours after he authorized an exploratory committee to start working on a possible campaign.

Hannemann is expected to attend a United States Conference of Mayors meeting in Rhode Island today.

Hannemann would face Abercrombie, who announced his plans to run for governor in March. The Hawaii Democrat is planning a June 29 fundraiser.

In 1986 Hannemann ran against Abercrombie for Congress and won the primary for the 1st District seat vacated by Cec Heftel, who left to run for governor. But Hannemann lost the general election to Republican Pat Saiki.

Then in 1990 Hannemann ran against former Rep. Patsy Mink and lost in the primary.

He first won public office in 1994, winning a seat to the City Council, and was re-elected in 1998. Then in 2000 he resigned his office to run for mayor against incumbent Jeremy Harris but lost.

Hannemann ran for mayor in 2004 and won against Bainum.