It’s a question that has perplexed even veteran political observers.

Why is a union-backed super PAC spending hundreds of thousands of dollars on advertising to back a candidate for a political office that has little power and that historically has not played a role in the union’s bread-and-butter issue, rail?

“I think that’s the central mystery of this election cycle,” said Colin Moore, director of the Public Policy Center at the University of Hawaii at Manoa.

“It’s extraordinary,” added Tom Coffman, Hawaii author and political historian.

Be Change Now, the super political action committee financed by the pro-rail Hawaii Regional Council of Carpenters, has spent nearly $461,000 on upbeat commercials that started running in early June backing Josh Green, a Hawaii island state senator, for lieutenant governor. The ads will continue until election day on Aug. 11.

Four other Democrats are running for the seat, which comes with few powers and responsibilities but historically has been a stepping stone to higher office: State Sen. Jill Tokuda, Kauai Mayor Bernard Carvalho, former Board of Education member Kim Coco Iwamoto and former state Sen. Will Espero.

Many believe the race already has become the most expensive primary fight for lieutenant governor in the state’s history. Evidence of that can be seen in the nightly onslaught of television commercials.

Don’t expect that to let up.

The candidates and the PACs supporting two of them — Green and Tokuda — are spending roughly $1.5 million combined on television, newspaper, radio and online advertising running mostly in the last month of the race, according to records filed with the Campaign Spending Commission. The bulk of that advertising is on television.

The University of Hawaii Professional Assembly, the faculty union, filed a report last week saying it spent nearly $70,000 on Tokuda advertising, most of it running that final month.

Adding to the perplexing nature of the super PAC’s spending on Green is the relatively small amount being spent on the organization’s choice for governor, U.S. Rep. Colleen Hanabusa, who is trying to unseat incumbent Gov. David Ige.

The person sitting in the governor’s chair is in a much better position to advance issues important to the union.

Yet the super PAC’s $461,000 expenditure on Green ads since early June is nearly six times what it has spent (roughly $80,000) for Hana­busa advertisements, according to online records the organization has filed with the commission as of Friday.

No other lieutenant governor candidate has attracted anywhere close to that level of outside ad support.

The $461,000 also is more than the amount three of the candidates have spent on their entire campaigns as of July 1.

That unprecedented level of independent spending on a lieutenant governor’s race has fueled speculation about the union’s motives.

Some campaign insiders, political observers and legislators say the super PAC’s backing is more about political retribution than rail support, job creation or the other issues important to carpenters.

“I think it’s a personal vendetta,” said Rep. Sylvia Luke, who noted that Tokuda clashed with the union over a rail bailout proposal last year at the Legislature.

Tokuda, Iwamoto and Espero, the most prominent rail supporter among the five candidates, didn’t get invitations from the union for its endorsement interviews.

Espero was a frequent critic of the Honolulu Police Commission for its lack of oversight of the police department during the period the panel was headed by Ron Taketa, the carpenter union’s top executive.

“He took it personally,” Espero said of the criticism.

Some also speculate that the union is hedging its bet, believing Green would make a strong gubernatorial candidate in 2022 should Ige win re-election this year. If Ige wins, he would not be able to run for governor four years from now because of term limits. If Green is the lieutenant governor, he would be in a good position to succeed Ige.

“It’s an investment, a down payment,” Coffman said of the union backing.

A spokesman for Be Change Now disputed the notion that the union was motivated by political retaliation.

“We support candidates we believe give Hawaii the best chance for positive, effective leadership,” said Eric Koch in written responses to Honolulu Star-Advertiser questions.

He said the lieutenant governor holds an important office and can work with the governor to provide that leadership.

“As a state senator, Josh Green has been a tireless advocate for Hawaii,” Koch wrote, explaining why the super PAC supports him. “He fought for our schools, worked to protect our environment and stood up for women.”

Asked about Espero’s long-time pro-rail support and Green’s vote against the bailout bill (Green has said it was unfair to neighbor islanders), Koch said “supporting or opposing rail is not the only criteria for selecting candidates to endorse.”

Koch did not directly address whether a factor in the Green endorsement was his potential as a gubernatorial candidate in 2022. But Koch did say the organization believes Hanabusa will win this year’s election.

Asked what the union expects to get in return for its investment in Green, Koch was blunt: “Nothing.” He also repeated the union’s desire for effective leadership.

Topping the poll

In the most recent Star-Advertiser Hawaii Poll this month, Green was the top pick among likely primary voters surveyed. Green received 34 percent support, followed by Tokuda and Carvalho at 14 percent. Iwamoto came in at 10 percent, and Espero tallied 6 percent.

When the same poll was taken in March, the race was a toss up. Green was favored by 19 percent of likely voters, Carvalho 14, Tokuda 12, Espero 9 and Iwamoto 5. The margin of error for both polls was 4.5 percentage points.

Several of Green’s opponents say Be Change Now’s spending has made a big difference.

“Without a doubt, these super PAC ads are influencing the outcome,” Iwamoto said in a statement to the Star-Advertiser. “This race was a toss up until the corporate-backed super PAC began this massive ad campaign.”

“Hawaii deserves better, and I’m not backing down even if special interests seeking to buy an election have a vendetta against me,” Tokuda said in a written statement.

Green declined to respond to questions about Be Change Now’s backing. Instead, he issued a written statement, saying he was honored to have strong support across the state. He said he believes “this election is about doing more to help Hawaii’s working families with better health care, better schools, higher wages and more affordable housing.”

His supporters note that Green’s campaign started advertising last fall, months before the newspaper polls were conducted. From September through June of this year, his campaign spent over $138,000 in Facebook advertising, according to commission records.

Koch dismissed criticism that the super PAC is attempting to “buy” the election.

“We give Hawaii voters more credit than many critics do,” he wrote. “We use TV, radio and digital ads to communicate with voters in support of Hawaii leaders who will work toward those goals. It is ultimately up to the voters on who they decide to vote for – and our efforts help them make informed choices.”

Unlimited backing

Be Change Now’s spending in the race underscores the changing political landscape since the controversial 2010 U.S. Supreme Court ruling known as Citizens United.

As a result of that ruling, corporations and unions are free to spend unlimited sums backing or opposing a candidate as long as they do so independently of the candidate.

More than any other organization in the state, the carpenters union has capitalized on that change to try to influence elections, political analysts say.

In 2012, Pacific Resources Partnership, a coalition of union carpenters and private contractors, spent more than $3.6 million to help defeat former Gov. Ben Cayetano in his bid to become mayor. Cayetano ran on an anti-rail platform.

Cayetano subsequently sued the organization for defamation, saying PRP’s ad campaign unfairly tarnished his reputation. The lawsuit was settled with PRP publicly apologizing to the governor and making $125,000 in charitable contributions on his behalf.

In this year’s lieutenant governor’s race, Be Change Now is taking a more positive approach, running ads meant to boost Green’s image, not attack his opponents.

Asked about the disparity in its spending for Green and Hanabusa, Koch said “there is still a lot of time between now and election day.”