Heading into the final month of the campaign, state Sen. Josh Green has substantially widened his lead over four other Democratic candidates for lieutenant governor, the latest Honolulu Star-Advertiser Hawaii Poll shows.

Some 34 percent of likely statewide Democratic primary voters said they would cast their ballot for Green if the election were held today, according to the poll, conducted last week by Mason-Dixon Polling & Strategy.

That gives the Hawaii island senator a 20-percentage-point lead over his two closest competitors, state Sen. Jill Tokuda and Kauai Mayor Bernard Carvalho, who both tallied 14 percent in the poll.

Undecided voters totaled 22 percent — enough to fuel hope among Green’s rivals — but that number was about half the level from the last Hawaii Poll in March.

Green showed the greatest percentage-point gain from March, when he scored 19 percent. His 15-point swing compares with Carvalho’s unchanged total and a 2-point improvement by Tokuda.

Former Board of Education member Kim Coco Iwamoto doubled her total from March, getting 10 percent in the latest poll.

Former state Sen. Will Espero, who resigned from his legislative seat in late May to focus on his campaign, saw his support slip to 6 percent, compared with 9 percent in March.

Green’s lead was evident not just in the statewide results, but in each breakout category, according to the poll. He was favored by men, women, Oahu and neighbor island voters.

Given Green’s significant war chest heading into the final stretch of the campaign, he is in a hard-to-beat position — barring a last-minute surprise before the Aug. 11 primary, according to one political analyst.

“It looks like Josh Green is pulling away,” said Todd Belt, a University of Hawaii-Hilo political science professor. “That’s all you can really say about this. … It’s his (race) to lose.”

The Hawaii Poll, conducted July 6-11 on cellphones and landlines, included 494 likely statewide Democratic primary voters. The margin of error is plus or minus 4.5 percentage points. The prior poll was conducted March 13-18. It included 498 likely statewide Democratic primary voters and had the same margin of error.

Several people who were polled last week attributed Green’s gains to his television commercials.

“I think he’s done a phenomenal job of advertising,” said retired Honolulu resident Karl Minke, 78, a retired UH-Manoa psychology professor who isn’t supporting Green. He said he probably would vote for Tokuda.

“I’m thinking Josh Green is kind of fresh and new and maybe he’d be better at it,” said Tana Hoefling, 69, a retail salesclerk from Waikoloa on Hawaii island.

Elizabeth Sweet, 74, a retired Neiman Marcus employee from Honolulu, counts herself among the 22 percent of undecided voters in the race.

“I don’t know anything about them,” she said of the five candidates.

But Sweet said Green’s name is more familiar than the other candidates’ because of his television ads, which she has seen multiple times.

To continue his ad campaign, Green has a financial advantage over his two closest competitors based on their war chests.

As of July 1 he had about $153,000 on hand, substantially more than any of the other candidates except Iwamoto, who had nearly $250,000, according to campaign finance records. But Iwamoto’s balance largely was due to the $442,000 that she has loaned her campaign this year, including $242,00 on June 27, the records show.

Among the other candidates, Tokuda had about $90,000 in cash as of July 1, Carvalho nearly $41,000 and Espero about $28,000, their finance disclosure reports show.

As the election gets closer, name recognition becomes even more important, especially in a race in which few voters understand what the lieutenant governor’s job entails, according to Belt.

With Green’s name recognition and sizable campaign fund, the other candidates face a “Herculean task” in trying to overtake him, Belt said. “But there’s always hope,” he added. “You never know what’s out there.”

Green said he was pleased by the poll results but wasn’t going to let up on his door-to-door campaigning down the stretch. “I’m deeply honored and grateful to have such strong support across the state,” he said.

The Star-Advertiser requested interviews with Tokuda and Carvalho, but neither made themselves available. Instead, their campaigns issued written statements.

“We began airing Jill’s message just as this poll was conducted but already we’re seeing the excitement and enthusiasm build and have heard from many in the community as we’ve continued to grow our strong grassroots campaign,” said Jadine Nielsen, her campaign co-chairwoman. “We expect this momentum will continue as Hawaii’s working families recognize Jill is fighting for a brighter future. After all, she shares their struggles as a working mom who comes from humble beginnings as the first college graduate in her family now living with three generations under one roof with everyone pulling together to make it work.”

Carvalho highlighted his background.

“Hawaii wants a leader they can trust,” his statement said. “So having a campaign that is inclusive and open to all has been an enormous blessing. There are two polls that matter to our team. The one we take every single day when we are out shaking thousands of hands all across our state and the one on Aug. 11th. I was born and raised in Hawaii, and I understand the values that we all hold dear. I’m the only candidate with executive level administrative experience and have spent my entire professional career serving the people of Hawaii and look forward to continuing to do so as lieutenant governor.”