The Roan Plateau in western Colorado is known for its natural splendor. Deep canyons and mountain streams cut across the aspen-forested landscape. Hunters, hikers and anglers prize the Roan for its large herds of mule deer, rare plants and cutthroat trout.

But there are resources below the Roan that some prize even more: fossil fuel. The plateau boasts the biggest nonleased reserve of federally owned natural gas outside of Alaska, according to David Boyd, a spokesman at the Colorado office of the U.S. Department of the Interior's Bureau of Land Management (BLM).

With energy becoming more and more expensive, drilling the Roan for natural gas would seem a win–win—at least to some: All that gas is expected to yield about half a billion dollars for the State of Colorado over the next twenty years. But many hunters, hikers and anglers fear that natural gas drilling will despoil the landscape. After all, that's what's happening in neighboring Wyoming.

There, seven years of natural-gas drilling in the Pinedale Anticline region have slashed mule deer populations by a third. Air and residential water quality have dipped as well, with the state issuing five ozone warnings—the first ever—earlier this year. "I don't think there's any doubt that there are lessons to be learned [in Colorado] from what's happening in Wyoming," says Hall Sawyer, a wildlife biologist with the consulting firm Western EcoSystems Technology in Laramie, Wyo.

Now a decadelong struggle over the fate of thousands of acres of public land on the Roan has come to a head, and just in time for the hotly contested race for Colorado's open U.S. Senate seat. Republican Bob Schaffer and Democrat Mark Udall are competing to succeed Wayne Allard, the retiring GOP incumbent. Udall has led Schaffer in most polls since the race began last summer and recent results put him ahead by high single digits, though roughly a quarter of Colorado's voters remain undecided.

Both candidates have run mudslinging campaign ads—Udall's are paid for in many cases by the League of Conservation Voters, whereas Schaffer's contributors include ExxonMobil and Halliburton—establishing their disparate positions. Some ads produced by advocacy groups outside the campaigns go beyond the issues into ad hominem attacks, labeling Schaffer as "Big Oil Bob"; a Web site shows a cartoon of him riding an oil well like a cowboy. On the other side, commercials mock Udall as a "Boulder liberal," and a recent ad paints him as a dope-smoking hippie.

A look at the candidates bios strengthens that impression: Schaffer, a former House member, is the former vice president of Aspect Energy, a company that focuses on developing oil fields in places like Iraqi Kurdistan. Udall, a five-term congressman, and son of Arizona representative and 1976 Democratic presidential contender Mo Udall, served as Colorado's executive director of Outward Bound, an outdoors adventure and awareness program, before he entered the political arena in the mid-1990s.

During their shared time as House members, they voted on opposite sides for oil drilling in national monuments, increasing automobile fuel efficiency, and on renewable energy, according to the Rocky Mountain News.

But do they really disagree that much on the future of the Roan?

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Earlier this year Colorado Gov. Bill Ritter (D) proposed allowing drilling on top of the Roan and around its base under incremental, phased leasing that would parcel out one plot for development at a time. The BLM rejected Ritter's proposal in the spring, instead going with an all-out lease with staggered drilling plans for the top of the plateau and less land set aside for special protection. Udall and other Democrats in Colorado's congressional delegation proceeded to sponsor legislation similar to Ritter's plan. Udall had also previously proposed a greater reliance on directional drilling, which limits the number of well pads that would dot portions of the Roan's landscape. Neither of these measures passed.

Over protests from conservation and citizen groups, on August 14 the BLM auctioned off energy leases for all of the remaining public land on the Roan encompassing 54,631 acres (221 square kilometers). The BLM estimates that some 8.9 trillion cubic feet (252 billion cubic meters) of natural gas lies under the Roan's rocks, or approximately enough to heat four million homes for 20 years.

The final management plan contains some innovative environmental conservation measures, like spacing the gas wells at least a half mile (0.8 kilometer) apart and limiting production to just one percent of the plateau's environmentally sensitive surface at a time. "Some of these things haven't been tried anywhere else," Boyd says.

But Jim Angell, lead attorney for the Oakland, Calif.–based public interest law firm Earthjustice, which represents a host of environmental groups suing the BLM, says this 1 percent stipulation is "an accounting trick. Once the land is under production, it will be for decades."

Democrat Tresi Houpt, one of three commissioners for Garfield County, which contains most of the Roan, is also skeptical that the landscape and wildlife will be adequately protected. "The Roan is one of our special places in Garfield County," she says. "I think people are stunned" that drilling will be allowed.

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In televised debates and through spokespeople, the candidates have consistently sniped at each other's vision for the Roan. Udall states on his Web site that he has fought the Bush administration's efforts to open up the Roan for drilling "because not every place that can support oil [and natural gas] drilling should be drilled in my view," the candidate says.

Schaffer says that the Roan is a "tremendous asset and opportunity for Colorado" and that he supports developing the plateau in a "responsible, environmentally conscious and friendly way" to access all its "clean-burning natural gas." He upbraids Udall and others for "delaying" drilling on the Roan and that Colorado should "move faster" on energy production.

Political scientist John Straayer of Colorado State University (C.S.U.) in Fort Collins says that "neither [has taken] an extreme position as they both know that such a position is political poison."

Still, Dick Wadhams, Schaffer's campaign manager, says their differences are stark: "Schaffer wants to develop the Roan's resources and Udall does not—that's really the essential difference between these candidates."

But that difference is not all that clear. Schaffer and Udall actually agreed to Ritter's proposal in principle, with Schaffer announcing his support in March. The Denver Post expressed surprise at the agreement, noting that each campaign still sought to smear the other candidate as a flip-flopper for arriving at the agreement. Such a back-and-forth broke out in a subsequent debate.

The Udall campaign says that its options for changing how drilling will proceed are somewhat limited now that the BLM has sold parcels of land. "What ended up happening is what [Udall] tried to prevent," says Udall campaign spokesperson Tara Trujillo.

Wadhams counters: "We think that the drilling [on the Roan] can be done in an environmentally sensitive manner that will mitigate the impact on wildlife."

How much any of these alleged differences will make in the senatorial race is unclear. In the Centennial State, as in national polls, the economy in general is the voters' chief concern. No one has conducted any polls specifically looking at the Roan drilling issue, says political scientist Robert Duffy at C.S.U. "My hunch is that [the Roan issue] probably helps Udall marginally," he says.

But Duffy notes that the energy issue as a whole has probably helped Schaffer. Greg Schnacke, CEO and president of the Americans for American Energy (AAE), a Lakewood, Colo.–based lobbying organization, agrees. "Clearly, those that are for more energy development are doing better in election polling today than those who are against energy development," Schnacke says.

"The Colorado public is of two minds," Straayer says. Voters support energy development "because the nation needs it and it is good for jobs and the economy." But Coloradoans do not want "too much or too fast, as we cannot risk our recreation economy, our scenic splendor, our water, our wildlife [or] our heritage."

Once the winning candidate gets to Washington, of course, his decisions will affect national energy policy, not just Colorado's.

"Udall would be far more aggressive on the alternative energy and conservation front," says C.S.U.'s Duffy, and, because the Democrats will almost certainly still control the Senate after this election, Udall would have more influence. "Schaffer, on the other hand, will be in the minority party, and his record on energy and environmental issues is quite clear. He would continue the delusional 'drill here, drill now' policies," Duffy says.

"As elected officials their positions will differ significantly," C.S.U.'s Straayer says. "On energy alternatives, offshore drilling and general environmental caution, they'll be on opposite sides."

On national issues, Udall has said he supports targeted tax relief for the middle class, ending the war in Iraq and proposes an "earned path" to citizenship for illegal immigrants, including paying back taxes and learning English. His Web site urges investment in renewable energy and "green technology."

For his part, Schaffer has said that he supports extending the Bush tax cuts, does not want the Iraq War to have a "date-certain" end, and does not want "amnesty" for illegal immigrants. Schaffer's Web site says he is also in favor of drilling in the Alaskan National Wildlife Refuge and offshore areas.

The relative success of the Republicans "drill, baby, drill!" slogan nationwide, however, has made Udall and "the Dems have to play ball on drilling," says political scientist Kyle Sanders at C.S.U. "That is, at least until after the election."