HARRISBURG, Pa. (WHTM) — President Donald Trump and Vice President Joe Biden used the word “fracking” 15 times during Thursday night’s debate, all because of another word that could determine the upcoming election: Pennsylvania.

Hydraulic fracturing — or fracking, as it is widely known — is the process of drilling into shale to release oil or natural gas.

“Fracking is basically an engineering technique that enables you to get oil and gas out of very dense rock, which people used to think was absolutely impossible,” explained Daniel Yergin, vice chairman of IHS Markit, a data and information firm, and author of the Pulitzer Prize-winning book “The Prize: The Epic Quest for Oil, Money & Power.”

For most of its decade-and-a-half history, interest in fracking was largely the preserve of industry insiders and those who oppose the practice on environmental grounds. It had outsized importance in states like Pennsylvania, which produces about 25 percent of the natural gas in the U.S. that comes from fracking, according to the U.S. Department of Energy.

Texas and North Dakota, on the other hand, lead the country in oil produced from fracking.

Supporters of fracking generally tout its economic benefits; opponents worry about environmental consequences. Supporters say opponents overstate the environmental costs while opponents argue supporters overstate the economic benefits, particularly the number of jobs created by fracking.

Trump, meanwhile, is an unequivocal supporter of fracking who accuses Biden — most recently in Thursday night’s debate — of opposing the industry. Biden denies that, saying he merely supports a transition to renewable energy, such as wind and solar power, which he believes could be complete by 2035.

In Pennsylvania, even many Democrats whose party nationally includes vocal environmentalists who oppose fracking, support the industry. One example: Rep. Conor Lamb, a Democrat, whose March 2018 special election victory in a Republican-leaning district near Pittsburgh, where fracking is more important to the local economy than in eastern areas of the state, was viewed by many analysts an early sign that Democrats might do well in the mid-term Congressional election later that year.

Separate from the question of how much more supportive Trump might be of fracking than Biden is the question of how much the difference matters, in terms of the industry’s future. Even Steven Winberg, the Department of Energy’s assistant secretary for fossil fuels and a Trump appointee, acknowledged that natural gas prices, which have trended down since 2008, have caused the industry to be a victim of its own success. Its efficiency, in other words, flooded the market, and this force might be at least as important as any policies emanating from the White House. However, Winberg said an important benefit of the low prices is the fact that the U.S. has become a net exporter of energy after long depending on foreign oil and natural gas. That reduced dependence, he said, increases national security.

Similarly, Yergin, the energy expert and author, agreed partly with the idea that economic forces could do more to determine the industry’s fortunes than political ones. But cautioned against carrying that logic too far.

“Policy and politics matter in terms of regulation,” he said. “Just look at the difference between Pennsylvania, where you can have fracking with economic benefits, and New York State, next door, where you can’t.”

A NewsNation/Emerson College poll of Pennsylvania, conducted earlier this month, showed Biden leading but Trump inching closer in a state both men desperately want to win. The vice president had a 5-point lead, down from a 9-point spread in August.