Candidates for governor in Colorado from each party speaking at an industry event in Denver on Wednesday, both expressed opposition to a likely ballot initiative that would significantly curtail oil and gas production in the state.

The opposition shows the influence and large economic footprint of the oil and gas industry in Colorado despite intense environmental and local resistance to increased development. Colorado, an important political battleground, is America’s fifth-largest gas-producing and seventh-largest oil-producing state.

Republican Walker Stapleton, "This is nothing more than a job-killing measure, plain and simple."

Democrat Jared Polis, "We can’t ignore the role that the oil and gas industry has played in our growth, or the significant wages and tax revenue it creates in our state. … But neither can we ignore the conflicts between homeowners and operators, between surface rights and mineral rights, between state government and local government."

The initiative would increase a buffer zone between buildings and future drilling from 500 feet to 2,500 feet, and expand it to other "vulnerable" areas, which could encompass rural areas. It's waiting for final state approval to make the ballot; backers are confident they have needed signatures.

The intrigue: Polis’ position represents a nearly 180-degree turn. He helped fund a similar initiative in 2014, only to back off as he and Gov. John Hickenlooper, a Democrat, agreed to create a task force, which hasn’t put concerns to rest as wells continue to pop up around neighborhoods.

Colorado is America’s fifth-largest gas-producing and seventh-largest oil-producing state. Layer on top of that a political battleground and a growing population colliding with an increasing number of wells, and it’s ripe for controversies like this.

This is the third attempt since 2014 to get such an initiative on the ballot, and it’s likely to succeed in at least getting a vote.

During a panel I moderated, one industry executive — Bill Crawford, chief financial officer of HighPoint Resources — said 70% of his firm’s acreage could be affected. The industry points to a state government agency study concluding the initiative could cut off as much as 85% of the state’s future energy development on non-federal lands.

The initiative would impose a 2,500-foot setback for oil and gas development from occupied buildings and other “vulnerable” areas, which could include rural areas. It's waiting for final state approval to be placed on the ballot, but backers are confident they have the needed signatures.

Anne Lee Foster, one of the initiative organizers, said in an interview Tuesday that despite several years of attempted compromise, including a taskforce set up in 2016 by Democratic Gov. John Hickenlooper, nothing has been done to address growing concerns among residents.

The lack of progress, she said, comes as environmental and public-safety accidents have been apparently increasing over the last year.

Some parties of interest who have spent decades hunting for oil across the Middle East, South America and Canada are betting that the next energy patch will be near here, in a remote stretch of craggy desert known as Asphalt Ridge.

They are trying something that has repeatedly failed in Utah: mining the state’s enormous deposits of oil sands, an arduous process of extracting oil from hard rock.

The two oversee Petroteq Energy, a Canadian company that aims to have the first commercially viable oil sands production in the United States underway here by early September.

Petroteq’s claims challenge the notion that oil sands mining is in eclipse. The heavy oil produced from oil sands is among the most carbon-intensive fuels, a drawback as concerns about climate change grow.

Even in Canada, where oil sands production dominates the energy industry, some major oil companies have written off or withdrawn their investments. The Keystone XL pipeline designed to carry the fuel to American refineries has been stalled by environmentalists with protests and lawsuits. They typically call oil sands “a carbon bomb.”

David Sealock, Petroteq’s chief executive, is undeterred. He likens his tiny operation — with its modular mixing vessels, rock crushers and conveyor belt — to a humble Lego set. But when he picks up a canister of newly processed oil, he smiles at the acrid odor. “That’s the smell of money,” he said.

“We have a very disruptive technology,” said Mr. Sealock, who has worked for Chevron in several countries and managed two oil sands companies in Canada. “There was a treasure chest here that didn’t have a key, and this technology is the key.”

He says what makes his operation different from larger and deeper Canadian mining operations and all the past failures in Utah is a cocktail of solvents that can separate oil from rocks at little cost and with no water or air pollution.

He and the other veteran executive, Jerry Bailey, say that their approach will be far cleaner than oil sands mining in Canada, which is more water intensive and leaves vast toxic tailing ponds.