“There is an argument that maybe the marketplace is working on its own,” said Jon Hurst, president of the Retailers Association of Massachusetts. “One could argue in the cities and towns where there was the most pressure to do it, they’ve already done it.”

A handful of retailers in Massachusetts, including national grocer Whole Foods, already offer a discount for customers who bring their own reusable bag.

In April, supermarket chain Stop & Shop started charging a 10-cent fee for paper bags, and the company has pledged to eliminate plastic bags from its checkout counters across the Northeast by July. When he first heard about the change, Hurst said, he remembered thinking it “kind of kills the bag ban and bag tax bill.”

Massachusetts and New Hampshire are the only two states in New England without a statewide plastic bag ban, even as lawmakers have been pushing for one in the Bay State since at least 2009.

This year, some lawmakers and environmental advocates aim to tie the patchwork of more than 150 individual regulations into a unified, statewide rule that would ban retailers from providing any single-use plastic bags, with a handful of exceptions, and would mandate they charge at least 10 cents for paper and reusable bags.

Alex Vai, campaigns coordinator for the Massachusetts Surfrider Foundation, said he feels more momentum behind the bans today than anytime since he first started volunteering with the organization in 2016, the same year a ban nearly made it into the state budget.

“It’s pretty obvious that there’s a lot of local energy and desire for this,” Vai said. “Over the last 10-plus years while this has been rolling along, the local laws have only been getting stronger and stronger, and setting a higher and higher floor for what the state should be able to achieve.”

Nearly half of the state’s 351 cities and towns have bag bans. A Globe analysis found the population in those communities adds up to about 69 percent of all residents statewide.

It’s a sea change from 2016, when the Massachusetts Senate passed a budget that included a provision similar to this session’s bill. At that time, around 30 cities and towns had enacted their own regulations, the Globe reported.

Today, that figure is closer to 160, including Boston, Worcester, and Springfield — the state’s three most populous cities — according to data collected by the Massachusetts Sierra Club.

“In a sense, we’re already there. We’re just trying to get the last third,” said Clint Richmond, a Massachusetts Sierra Club executive board member.

Specific regulations vary from city to city and town to town, leaving a patchwork for retailers to navigate, especially those with locations across municipal borders, according to Brian Houghton of the Massachusetts Food Association, which represents grocers across the Commonwealth.

“When you get a big [retailer] that’s got 100-plus sites across the state, it gets pretty tedious,” Houghton said. “A fee here, a ban there, a certain amount of plastic . . . some allow compostable, which can’t be mixed into other plastic bags for recycling. It’s lot of issues going on, so it gets difficult to deal with these things on a state level.”

He said that piecemeal approach was probably one driver of Stop & Shop’s and other retailers’ moves away from plastic bags and toward a single, company-wide policy.

The proposed restrictions in the Legislature would not apply to bags used to carry prescription medication, some perishable and frozen food, or small items that could otherwise be lost, as well as bags “protecting articles of clothing on a hanger” given by retailers. The law would also carve out exceptions for nonprofits distributing groceries and clothing at a reduced cost, and for customers paying with an electronic benefits transfer card, more commonly known as EBT.

State Representative Mindy Domb, who is a key sponsor of the House bill, said she sees the disparities play out across her district. A CVS Pharmacy in Granby stocks plastic bags, she said, while another location in Amherst — less than 10 miles away — only offers paper. Meanwhile, some of her constituents are, by now, so used to local bans that they assume a state mandate must already be in place, she said.

Domb said creating a unified set of standards would ease confusion among merchants and customers, and it would help reduce feelings of economic competition between cities and towns with different bag standards.

In its current form, the bill would not prevent local municipalities from enforcing their own, stricter bans or heightened fees, though, so some of that competition may linger.

Senator James Eldridge, the bill’s original sponsor in the Senate, said he is confident the bill would clear the Senate, but its fate in the House is murkier, although he noted that an increasing number of legislators in the House represent communities with bans already in place.

“The Senate is very comfortable to take action,” Eldridge said. “I do feel like there’s growing support amongst the House.”

Daniel Kool can be reached at daniel.kool@globe.com. Follow him on Twitter @dekool01.