Stephanie Vasquez, owner of Fair Trade Coffee in Phoenix, says part of a $12 minimum wage is treating people “with respect and dignity.”

PHOENIX — Backers of a proposal to raise the state’s minimum wage to $12 an hour by 2020 claim they’ve already got more than half the signatures they need, potentially setting the stage for an expensive fight with restaurants and other businesses.

Tomas Robles said Tuesday the campaign he is heading has 90,000 signatures in hand. But he conceded it will likely need far more than the minimum of 150,642 names on petitions by the July 7 deadline to ensure the measure goes on the November ballot.

Robles said the group has at least $200,000 to supplement its volunteers with paid circulators to more than meet the goal.

That would provide voters the first opportunity to update the law they approved in 2006, which created a $6.75-an-hour state minimum wage the first year, when the federal government said employers could pay as little at $5.15.

With inflation adjustments required by voters, Arizona’s minimum wage is now $8.05 an hour versus the $7.25 federal minimum. Presuming 2 percent inflation per year between now and the end of the decade, Arizona’s figure still would be below $9.

The 2016 initiative contains something new: A requirement for paid sick leave of 40 hours a year for employees of companies with 15 or more workers. For smaller firms, the paid time off would be 24 hours.

One thing will be different this year than a decade ago. At that time the business community, confident a state like Arizona would never vote to increase wages, didn’t bother to mount a campaign against the 2006 initiative. The result was a blowout, with the measure passing by a margin of close to 2-1.

Glenn Hamer, president of the Arizona Chamber of Commerce and Industry, said Tuesday that business interests won’t make that mistake again.

“I would expect you’d see a very strong response to this, and a very broad response from chambers, major trade associations like the (Arizona) Restaurant Association to fight this should it qualify (for the ballot),” he said.

Hamer said the change would be particularly damaging for small businesses, which would be forced to provide immediate wage increases that could amount to $3 an hour.

He said that is coming on top of increased costs for health insurance for firms that provide such benefits to their workers. “Some simply won’t be able to survive,” he said.

But proponents are hoping to counter that by building a coalition of small businesses that say they can live with a $12 minimum wage.

At Tuesday’s news conference, one of the members, Stephanie Vasquez, owner of Fair Trade Coffee in Phoenix, detailed her support.

“I deeply believe that as an entrepreneur and as a human being that people should be treated with respect and dignity,” she said. Vasquez said the majority of her staffers already are being paid more than the $12 the initiative would mandate.

Arizona’s current $8.05 minimum wage translates to $16,744 a year.

For a single person, the federal government considers anything below $11,880 a year to be living in poverty. That figure is $16,020 for a family of two and $20,160 for a family of three.

Robles, former executive director of Living United for Change in Arizona, said that organization has put $200,000 into the campaign, much of it from a grant from The Center for Popular Democracy, an organization involved in efforts to establish a $15 minimum wage nationally. Campaign-finance reports also show $25,000 from The Fairness Project, which is working to push states to set minimum wages.