Former U.S. Rep. Neil Abercrombie and former Honolulu Mayor Mufi Hannemann might be knotted in the Democratic primary for governor, but both Democrats hold double-digit advantages over Lt. Gov. James "Duke" Aiona, the leading Republican, in hypothetical matchups for the November general election, a new Hawaii Poll has found.

Hannemann had a 54 to 37 percent cushion over Aiona with 9 percent undecided. Abercrombie had a 53 to 41 percent edge over Aiona with 6 percent undecided.

The margins were similar in a Hawaii Poll taken in late April.

"They both have very substantial leads, and Aiona has got a tough road ahead," said Rebecca Ward, president of Ward Research, which conducted the poll for the Honolulu Star-Advertiser and Hawaii News Now. "Either Democratic candidate, at this point, looks comfortably ahead of Aiona."

The poll was taken by telephone from Aug. 10-17 among 604 likely voters statewide. The margin of error was 4 percentage points.

Aiona has a primary against John Carroll, an attorney and former state lawmaker, but his campaign has been setting the pieces in place to build for the general election. The lieutenant governor has outlined public-policy positions on the economy and education but he has not tried to engage Abercrombie and Hannemann as the two Democrats command the attention of voters before their primary.

The Republican Governors Association has financed television advertisements to keep Aiona’s name in the mix, while Aiona is waiting to launch his own aggressive ads. The winner of the Democratic primary will likely deplete much of his campaign money in September and will have to reload to take on Aiona.

The Hawaii Poll found several positives for Aiona. He leads Abercrombie and Hannemann among independents, as he did in the last poll in April. He also is doing well among Hawaiians.

Aiona’s favorability rating is also equal to that of both Democrats. Fifty-seven percent said they have a favorable opinion of Aiona, while 31 percent have an unfavorable opinion. Independents rated Aiona higher than Aber-crombie and Hannemann.

Aiona must attract independents and moderate Democrats because the Republican base in the islands — about a third of voters — is not enough of a springboard.

Aiona had help over the weekend from an unlikely source when former U.S. Rep. Ed Case endorsed Abercrombie in the Democratic primary and offered a damning assessment of Hannemann. Case, a moderate who appeals to independents, said both Abercrombie and Aiona are "honest, independent, experienced candidates capable of governing competently and inclusively."

"It would be a singular achievement for us all to vote in the Democratic primary to reject the brand of fear-based exclusionary machine politics practiced by Hannemann, and to then each and all make an issues-based choice between Abercrombie and Aiona in the general election," Case wrote in an e-mail to his supporters on Saturday.

The Hannemann campaign said yesterday that Case’s "hateful e-mail assassinates the character of Mufi Hannemann with accusations that are completely devoid of any facts."

The Aiona campaign has private polling that shows hypothetical matchups against Abercrombie and Hannemann are much closer than the Hawaii Poll.

"This poll is geared toward an electorate preparing for a contentious Democratic primary election, and does not accurately reflect the coalition of Republicans, independents and moderate Democrats we’re cultivating to achieve victory in November," Travis Taylor, a spokesman for the Aiona campaign, said in a statement.

"Without putting up any ads, Duke Aiona already leads among independents and attracts the best favorability numbers among his potential opponents."

Thomas Taflinger, a police officer who lives in Mililani Mauka, said the state is too dominated by Democrats and needs political balance. He said he believes Aiona would be less likely to raise taxes and would be more careful about government spending.

"I know our state is Democratic — it’s been that way for a while — but there’s got to be balance," he said.

Ashley Tanaka, a part-time health aide at public schools who lives in Kapolei, said she feels she can relate to Aiona as a family man. Aiona, a former family court and drug court judge, has described strengthening families as one of the five core themes of his campaign. The other themes are clean energy, economic growth, public safety and education.

"You know how you meet some people and you just get a vibe?" she said. "You kind of get a sense that he’s not just for himself."