AUGUSTA — Mainers could take to the polls in 2016 to decide whether to raise the state’s minimum wage to $12 per hour by 2020.

The referendum campaign, spearheaded by the Maine AFL-CIO and the progressive Maine People’s Alliance, was kicked off Thursday, when the group turned in the signatures necessary to begin the process for a ballot question.

The plan would increase Maine’s minimum wage, currently $7.50 per hour, to $9 per hour in 2017 and by an additional dollar per hour each year until 2020. After that, the state’s minimum wage would rise or fall based on the cost of living, though it’s not immediately clear what measure would be used to determine that.

MPA has said a living wage for a single adult in Maine is about $15.82 per hour and that more than half the job openings in Maine pay less than that.

“For every job that pays $15.82, there are 12 job-seekers on average,” MPA’s political director Ben Chin said when he testified in favor of legislation to raise the minimum wage in March.

“The most basic premise of the American economic social contract is that you can work 40 hours a week and make ends meet. Our minimum wage of $7.50 an hour for non-tipped workers doesn’t get an individual even halfway there — let alone their families,” Chin said.

The groups took the first step Thursday toward getting the wage hike to voters. Next, they’ll need to collect more than 60,000 signatures to secure the referendum’s place on the ballot in 2016.

The Maine AFL-CIO has named raising the minimum wage as one of its top priorities this year.

In a news release announcing the referendum campaign Thursday, the labor group’s executive director, Matt Schlobohm, said the minimum wage is no longer enough to live on.

“The costs of groceries, childcare, housing and other basics have gone up for years, but wages haven’t come close to keeping up,” he said. “This is about seniors who can’t retire and parents working endless hours away from their families. Working people deserve fair wages. They deserve work with dignity, and they deserve better than poverty for full-time work.”

In an election cycle that often seemed dominated by calls for welfare reform and tax cuts, increasing the minimum wage was one cause championed by Democrats and other progressives that resonated with voters, with national and Maine-based polls indicating broad support for an increase.

Several large businesses, such as Walmart and McDonald’s, voluntarily have increased their own minimum wages recently in a move that could indicate a recognition by large employers of increased public pressure for higher wages.

But not all businesses agree. The Maine chapter of National Federation of Independent Businesses voiced their opposition, saying the move would be too costly for employers, especially small businesses.

“Regardless of their motives for doing so, even a seemingly modest increase could be terrible for business and will disproportionately affect small employers,” David Clough, NFIB Maine State Director, said in a written statement in March.

In 2013, legislative Democrats passed a bill that would have hiked the state’s minimum hourly wage to $9.50 incrementally over three years, but the bill was vetoed by Gov. Paul LePage. Legislative Republicans voted to sustain the veto.