Two big Alaska unions on Wednesday announced their support for repeal of the oil tax cut in next week's referendum, signaling a split in the Alaska labor movement on the issue after four other major unions joined the coalition opposing repeal in June.

The new announcements, by International Brotherhood of Electrical Workers Local 1547 and the Alaska State Employees Association, came with pledges of $20,000 from each union to the cash-strapped but volunteer-rich Vote Yes campaign. The election is Tuesday, and a big group of Vote Yes! Repeal the Giveaway volunteers were at the IBEW union hall in Midtown Anchorage for the announcements.

In June, four blue-collar unions that formed the backbone of the trans-Alaska pipeline construction workforce and which continue to work in the oil industry said they opposed the referendum. An official of one of those unions, Teamsters Local 959 secretary-treasurer Rick Boyles, is one of the statewide co-chairs of Vote No on One, the leading opponent of the referendum.

Those four unions -- Teamsters, Plumbers & Pipefitters United Association Local 375 in Fairbanks, Operating Engineers Local 302 and Laborers Local 942 -- call themselves the North Slope Pipeline Unions. While they haven't contributed cash to the Vote No campaign, they've sent officials to speak at events and to film commercials and have had members volunteering in the "ground game" get-out-the-vote effort, said Willis Lyford, Vote No on 1 campaign director.

The politically active state AFL-CIO, with headquarters next door to the IBEW, was noticeably absent from the Wednesday announcements. Mike Hodsdon, business manager of the IBEW local, said he still hoped to convince the statewide labor umbrella group to endorse the yes side.

But with a two-thirds vote needed in the Alaska AFL-CIO governing body to pick a side on a referendum, that wasn't likely, said Alaska AFL-CIO president Vince Beltrami.

"The unions are split," Beltrami said by phone. "It's really a divisive issue. There are people with good intentions on both sides of the issue."

The AFL-CIO will save its bullets for the November election, when the ballot will include the U.S. Senate race, repeal of the city's labor ordinance and dozens of legislative races, Beltrami said.

A no vote on Ballot Measure 1 in Tuesday's primary will spare Senate Bill 21. That tax law, named the More Alaska Production Act, was passed by a deeply divided Legislature in 2013 to reduce oil taxes and encourage the industry to spend more and pump more oil.

A yes vote will repeal SB 21 and restore the 2007 tax law known as ACES, or Alaska's Clear and Equitable Share. Supporters of ACES say it encourages independent oil companies to drill in Alaska and gives the state a bigger share of the produced oil wealth than does SB 21, especially when prices are high.

Vote No, supported with millions of dollars in contributions from the oil industry, has outraised the Yes forces by about 100 to 1.

A new Vote No ad on the Internet that was designed to catch attention may be getting too much of it. The photograph shows a busty woman in a low-cut shirt and tight shorts, heavily made up with tattoos across her chest and biceps. She has pouty red lips and a chain saw in her hands. "Bad idea: New assistant," the ad copy reads. And a good idea? Voting no on 1, the ad says.

The ad, which showed up on websites viewed in Alaska, was shared Wednesday on Twitter feeds and emails, mostly from angry Vote Yes supporters. It was the brainchild of one of the smaller Vote No groups, Keep Alaska Competitive -- Vote No on 1, an organization made up of oil-field contractors, Northrim Bank, Lynden Transport, GCI and other businesses.

"I don't even think of it as a stereotype -- it's just a humorous ad," said Jeanine St. John, the group's campaign manager. "We came up with this creative idea of what's a bad idea and what's a good idea. ACES is a bad idea and tax reform is a good idea, so we're just trying to get attention with our ads and there's a whole series of them coming out. They should be a lot of fun."

The endorsements of the Yes campaign by the IBEW and the state employees union wasn't a big surprise. State workers benefit from high oil taxes, while SB 21 may require significant budget cutting. One of the leading opponents of SB 21 is Sen. Bill Wielechowski, D-Anchorage, who's also an IBEW attorney. Another SB 21 opponent, House Minority Leader Chris Tuck, D-Anchorage, is an IBEW organizer.

Hodsdon, the IBEW business manager, said it took his union a while to reach consensus on the issue.

"We took our time doing a lot of due diligence to research the facts and give careful consideration to all sides of this issue, and that's why we've come to the conclusion that we have, that this is not in the best interests of the state and the working people that we represent, or the state's economy," Hodsdon said. "It was the due diligence process that took us so long."

Beltrami said the two unions in the Wednesday endorsement of Yes represent about 14,000 Alaska workers, while the trade unions in the June endorsement of No represent about 8,000.