A diverse and powerful coalition made up of unions, businesses and environmentalists are working together to urge residents to vote ‘no’ in the general election on whether to hold a state constitutional convention.

The coalition, called Preserve Our Hawaii, has registered with the Hawaii Campaign Spending Commission as a ballot measure committee and can raise and spend unlimited funds in its effort to defeat the measure on Nov. 6.

The coalition includes many of Hawaii’s major unions, such as the Hawaii Government Employees Association, which is the state’s largest, and unions representing public school teachers, police and firefighters. The Chamber of Commerce of Hawaii, the Sierra Club of Hawaii and the Hawaii chapter of the American Civil Liberties Union have also joined in the coalition, as has the Hawaii Democratic Party. The party’s state central committee voted unanimously last month to oppose a convention.

“The groups coming together in opposition of a constitutional convention don’t always see eye-to-eye,” said Randy Perreira, HGEA’s executive director, in a press release on Thursday. “However, we all recognize that Hawaii’s Constitution is one of the best in the country and a ConCon could very well weaken the rights and protections that we have today.”

Gary Hooser, vice chair of the state Democratic Party’s Central Committee, said there’s too much at stake when it comes to environmental and labor protections, in particular, to open the state Constitution to revision. A well-known leader among Hawaii progressives, Hooser said a convention is an enticing way to try to push forward reforms that have stalled in the Legislature. But he said chances are slim for achieving progressive reforms, in part because the Legislature would set the parameters for electing delegates and the rules of the convention.

“To risk everything on a maybe, a very slim maybe, a very romantic and enticing maybe — it is too much to risk at the end of the day,” said Hooser.

Residents are given the chance to vote on whether to hold a state constitutional convention every 10 years. The last convention was in 1978 and ushered in major environmental protections, created the Office of Hawaiian Affairs and term limits for governor, as part of the three dozen amendments that were ultimately approved by voters.

The groundswell of opposition from organizations that could stand to lose something if the state’s Constitution was reopened for revision mirrors efforts made the last time the question was posed to voters. In 2008, groups opposing what is commonly referred to as a ConCon spent $1.4 million, according to the Hawaii Campaign Spending Commission. By contrast, ballot measure committees supporting a convention spent just $6,000. The convention was defeated 62 percent to 34 percent, with about 4 percent of voters leaving the question blank. Blank votes count as ‘no’ votes.

It’s not clear yet how much has been raised or spent this year in an attempt to defeat the ballot measure. The next filing date for noncandidate committees to disclose their finances isn’t until Oct. 29, after early voting is well underway. However, Preserve Our Hawaii has launched a television ad and created a website called “Don’t Be ConConned,” in which they make three main arguments: that a convention would be too expensive, too dangerous and entail too many unknowns.

The coalition warns that mainland special interest groups could pour money into the process in an attempt to advance their agendas and that approving a ConCon could weaken protections for the environment, civil rights, Native Hawaiian rights, collective bargaining, public employee pensions and health care. A ConCon is estimated to cost $56 million, according to the Legislative Reference Bureau.

While organizations are banding together to oppose the ballot measure, there doesn’t appear to be any comparable organized effort to drum up support for a constitutional convention, although individuals such as Sen. Laura Thielen and Ikaika Hussey, a magazine publisher and community advocate, have publicly expressed their support.

“A state constitutional convention is the time for citizens to discuss big ideas that create a brighter future for Hawaii. The opportunity for citizens to make sure government is working for all, not just a favored few. The only way citizens can require government to address chronic, difficult issues it ignores, pays lip service to, or seems incapable of resolving on its own,” wrote Thielen in a blog post supporting a convention earlier this month.

Thielen argues that a ConCon could be used to address the lack of affordable housing in Hawaii, make the Legislature abide by the Sunshine Law, which it has exempted itself from, and reform campaign spending laws.

There have also been neutral efforts to educate voters on the pros and cons of a convention, including a “citizen’s jury” that was organized by Keith Mattson, a public policy researcher, and Colin Moore, director of the Public Policy Center at the University of Hawaii at Manoa. The group included 18 members from the public who released a statement this week on their findings.

Jury members supporting a convention said it would reestablish public trust in government by allowing active participation by citizens, allow delegates to take a comprehensive approach to improving government, provide an opportunity for imposing term limits for state legislators and other reforms and clarify Native Hawaiian rights. It would also allow voter initiatives and referendums to be placed on the state ballot.

Jury members opposing a ConCon reiterated many of the concerns of Preserve Our Hawaii. The jury added that Hawaii voters are unlikely to put effort into becoming sufficiently informed on proposed amendments that emerge from the convention, which they would then need to vote on. They said a convention also may not be worth holding until Hawaii residents hold elected officials accountable for following what is currently already law.

Mattson, who says he is neutral on the issue, said that while certain protections could be tinkered with during a convention, he didn’t think it would result in any major scaling back of traditional rights.

“Hawaii is fundamentally a progressive state and a state that is very conscious of rights, and I would personally find it hard to believe that a fundamental right that has been enjoyed for 40 years or more would be taken away totally,” said Mattson. “That strikes me as a little bit beyond what I would consider Hawaii voters would approve.”