On a cool and sunny day in the middle of last month, the head of the Sierra Club’s Pennsylvania chapter stepped to a microphone on the steps of Penn State’s Old Main to warn a group of 100 protesters about the environmental dangers created by the recent surge in natural gas drilling across the state. “We are under assault, we’re under attack by invaders from Texas, from Oklahoma,” the advocate, Jeff Schmidt, told the crowd. “Range Resources and Chesapeake and Anadarko and other companies are not going to be satisfied until they have all the gas rights in Pennsylvania.”

The rally was the prelude to a march on an industry drilling conference sponsored by the university and several natural gas companies. The Sierra Club is vowing to use the 2012 campaign as a way to educate the nation about the pollution and land-use effects linked to shale gas drilling — and to use one of the biggest swing-state prizes as its classroom. To that end, the group is working to organize local citizens’ organizations to protest at every industry conference in the state until Election Day.

The issue of hydraulic fracturing — known as fracking — wasn’t even on the political radar in the last presidential race, but it now stands to be one of the principal parochial concerns on the minds of thousands of voters next fall. And the bulk of them are in Pennsylvania, which President Barack Obama expects he’ll have to work very hard to carry next year — even though he won it by a comfortable 10 points last time, bringing the Democratic nominees’ success streak in the state to five.

In simple terms, Democrats win in the state when they pile up huge margins in Philadelphia and Pittsburgh, and Republicans win when they put up even more lopsided victories everywhere else. That means that, in a close election, the outcome could turn on how the fracking issue plays out in the rural expanses atop so much of the natural gas.

The president has made it clear that he supports fracking as a way to increase domestic energy production and create jobs. But he has been vague on whether regulation of the industry should be steered toward the states — which is what the drillers prefer — or his administration should impose more federal air and water pollution controls on the procedure, a move environmentalists say is essential but which the industry contends would hobble the pace of development and the hiring of thousands.

The Republican presidential candidates, meanwhile, have all made it clear that they have no interest in putting the Environmental Protection Agency in the business of fracking oversight. “We’re standing on top of the next American economic boom, and it’s the energy underneath this country,” Texas Gov. Rick Perry said in Pittsburgh in October. “The quickest way to give our economy a shot in the arm is to deploy the American ingenuity to tap American energy. But we can only do that if environmental bureaucrats are told to stand down.”

Question of Oversight

Fracking uses a high-pressure injection process to force water, sand and chemicals into rock a mile or more below the earth’s surface. Once the rock is cracked, the water is extracted and natural gas that was trapped in the shale rock can flow to the surface. In Pennsylvania’s case, the rock at issue is the Marcellus Shale formation, which stretches across three-quarters of the state and extends from southern West Virginia to upstate New York. The government estimates the shale holds 410 trillion cubic feet of natural gas, enough to heat the nation’s homes and cook its food for 17 years.

Since fracking was first introduced in Pennsylvania in 2004, officials have granted permits for more than 7,000 wells. Some dying hamlets have been transformed into boom towns by workers flocking to drilling sites. The development has clearly helped hold down the state’s unemployment rate; it was 8.1 percent in October, when 26 states had higher rates and the national figure remained at 9 percent. Those numbers give industry officials confidence they will win the debate next year over the relative merits and drawbacks of fracking. “When we look at the 2012 elections, head and shoulders above everything else is going to be the role that job creation plays,” said Kathryn Klaber, president of the Marcellus Shale Coalition, an alliance of 250 natural gas industry companies.

But many voters worry that all those chemicals being forced underground will create serious and lasting environmental damage. Local activists say there is solid evidence that toxic materials used for fracking have ended up in rivers and in drinking water wells near drilling sites. They also lament that all the heavy drilling equipment has ruined local roads and devastated the landscape.

Since the fracking boom began, state regulators have handled oversight of the industry’s safety and environmental practices. But as fracking escalates in Pennsylvania and other states, a growing number of energy experts say more aggressive controls are needed. A study last month by an Energy Department advisory panel warned that if action is not taken to reduce the environmental effect of shale gas drilling, “there is a real risk of serious environmental consequences and a loss of public confidence that could delay or stop this activity.”

Federal regulators are already stepping up their oversight. The EPA recently announced plans to require energy companies to clean up any fracking water that is destined for local sewage plants. Regulators note that those facilities aren’t equipped to filter the salts, toxic chemicals and radioactive materials that are fracking byproducts. The agency also wants drillers to disclose which chemicals they inject into the earth — so it can be aware of toxins that could foul drinking water supplies or prompt fishkills.

Energy companies are fighting those regulatory plans, arguing they have already promised not to send their fracking wastewater to local sewage plants. And after years of resisting disclosure of their chemical recipes, the companies now say that early next year they will start making public the roster of the toxic substances they inject into their wells.

Potentially more important to the 2012 presidential race is the ongoing debate over proposals to allow shale gas drilling in the upper Delaware River Basin in the Pocono Mountains where Pennsylvania, New York and New Jersey come together. Citizen groups are worried that fracking in the region could contaminate the watershed and the river, which provides drinking water to more than 15 million people including the residents of Philadelphia.

Economic activity in the region is governed by the Delaware River Basin Commission — the four governors with parts of the basin in their states and an Army Corps of Engineers official. Last month, the panel postponed a vote on whether to lift a moratorium on natural gas extraction in the region. Indications were that the governors were split, which would have put the Obama administration in the politically sensitive position of casting the deciding vote. The panel has not yet announced when the issue will be reconsidered.

Public Opinion Varies

Environmentalists are using the Delaware River proposal to rally opposition to fracking. Their aim is to elevate the issue onto the national political scene, much the way activists in the Midwest gained national headlines in the fall about the potential hazards of allowing TransCanada to build an oil pipeline across the environmentally fragile sand hills of Nebraska — and influenced Obama’s decision to effectively postpone a decision until after the election.

In Pennsylvania, energy companies have been snapping up the drilling rights for property and getting more involved in local politics. In the past three years, they have spent $5 million lobbying in Harrisburg and given $7 million to candidates across the state. One result is that polling shows the state generally behind shale gas extraction. In one survey this fall, by Mercyhurst College in Erie, 55 percent of Pennsylvanians said they favor the fracking boom — although a clear majority also favored stricter environmental oversight. Beyond that, the poll showed how natural gas development “is one of the most important issues facing Pennsylvania,” Mercyhurst’s Joseph M. Morris said.

Public sentiment about fracking varies across the state. Voters in the rural western, central and northern parts of the state, where the natural gas industry dominates local economies, are solidly in favor of it. “Marcellus Shale drilling has brought such economic development to western Pennsylvania that virtually no politician that wants to get re-elected is going to hurt his or her chances by saying that fracking is dangerous or that there have been accidents,” noted political scientist Joseph DiSarro of Washington & Jefferson College.

But environmental concerns are growing in the two big metropolitan areas and in Centre County (where Penn State is located), one of the few counties in the middle of the state that Obama carried in 2008. “Pittsburgh gets its drinking water from the Allegheny and the Monongahela rivers, and there have been a lot of issues with contaminants from drilling getting into those two rivers,” said Myron Arnowitt, Clean Water Action’s Pennsylvania director. “I think there is the potential for this to become a serious issue in 2012.”

In the Philadelphia area, which is outside the Marcellus Shale region, voters tend to worry more about the potential effects of drilling on local air quality, drinking water and rivers. In those regions, a Republican presidential candidate could actually lose votes by attacking the EPA, said Joshua McNeil, executive director of the Conservation Voters of Pennsylvania.