(Adds details on storm information, background)
By Malia Mattoch McManus
HONOLULU, Aug 9 (Reuters) - Hawaii voters went to the polls on Saturday for the state's primary election as local authorities and residents rushed to clean up debris from one tropical storm with only a day to prepare for an approaching hurricane.
Voters are to decide a Democratic primary contest between Governor Neil Abercrombie and state Senator David Ige. The governor has a thriving economy on his side, but Ige has surged to a double-digit edge in polls despite raising a fraction of Abercrombie's campaign war chest.
A loss by Abercrombie, who was endorsed by Hawaii-born President Barack Obama, would mark the first defeat for an incumbent Democratic governor in Hawaii since it was granted statehood in 1959, potentially upsetting the political landscape ahead of the U.S. general election in November.
This week, Abercrombie declared he was taking a break from campaigning to deal with the approach of Iselle, but his frequent television appearances to discuss disaster preparedness could help his candidacy.
"The governor got a lot of free airtime," said Chad Blair, a political reporter at Civil Beat and a lecturer at the University of Hawaii at Manoa. "He was in his commander-in-chief role, very much leading the state's response to ... Iselle."
All but two polling stations on the east coast of the island of Hawaii, also known as the Big Island, opened on Saturday morning, election officials said.
Iselle weakened from a hurricane to a tropical storm before it struck the Big Island on Thursday and later lost more force as it pushed past the U.S. state.
As thousands of residents scrambled to clear away debris from the storm, officials warned against complacency given the extent of the disruption and the uncertainty over the path of the bigger storm hurtling toward them.
Hurricane Julio, which was downgraded to a Category 2 storm on Friday, was packing maximum winds of 100 mph (155 kph) as it churned about 415 miles (668 km) off the Big Island city of Hilo and 685 miles (1,100 km) east of Honolulu, the state capital, the National Weather Service said early on Saturday.
Forecasts showed Julio likely tracking about 250 miles (402 km) northeast of Hilo on Sunday morning, meteorologists said.
"Gradual weakening is forecast during the next couple of days, but Julio is forecast to remain a hurricane through Sunday night," said a Weather Service advisory.
There were no reports of major injuries from Iselle, a relief to a state heavily dependent on tourism. Some 95,000 tourists were visiting Oahu, the state's most populous island, when Iselle hit.
The American Red Cross early on Saturday closed its shelters, where more than 150 people had spent the night and where about 2,000 people took refuge at the height of the storm, a spokeswoman for the group said.
About 9,200 power customers on the Big Island are still without power, a utility company said, warning that some customers could experience extended outages into next week or much longer.
"Iselle caused extensive damage to power lines and utility poles and crews are still assessing the damage," the company said.
Election analysts said that it was unusual for an incumbent governor to struggle given a strong economy, unemployment near a record low, tourism going well and sound state coffers.
A late July poll of 458 likely voters conducted for the Honolulu Star-Advertiser put Ige well ahead of fellow Democrat Abercrombie at 54 percent to 36 percent.
Abercrombie told supporters in a statement that Hawaii polls historically have often failed to presage actual results.
Supporters say Abercrombie has achieved much, signing gay marriage legislation into law, helping to negotiate a North Shore land conservation deal and championing development in downtown Honolulu. He also represented Hawaii in the U.S. House of Representatives from 1990 to 2010.
Ige's campaign issued emails urging voters to cast ballots early because of the storms.
Abercrombie in an email to supporters on Saturday also urged them to vote.
"At times, I've had to make difficult decisions that weren't always popular," he wrote. "But through it all, I have strived to keep your interests at heart."
The winner of the contest on Saturday will face Independent and Republican candidates in November's general election. (Additional reporting by Alex Dobuzinskis in Los Angeles and Ken Wills in Kapaau, Hawaii; writing by Eric M. Johnson; editing by Edith Honan, G Crosse and David Gregorio)