The Washington Post suggests a possible reason for the victory:
The environmental community scored a string of successes Tuesday in New Mexico, Montana, Texas and other states, winning seven of eight targeted Senate races and at least three targeted House races. Although plenty of outside groups poured money into these contests, even some representatives of the fossil-fuel industry said that environmentalists had invested their resources wisely in 2012. …One analyst gave his take on that New Mexico race to the Post:
The League of Conservation Voters (LCV) spent more than $14 million this year, more than it had in the past three election cycles combined, and groups including the Sierra Club, National Wildlife Federation Action Fund, Defenders of Wildlife Action Committee, Environment America and Natural Resources Defense Council Action Fund also devoted money and volunteers to key contests.
Political analyst Stuart Rothenberg, who had rated the New Mexico Senate contest as a tossup/tilt Democrat at the start of the summer, questioned whether environmentalists were decisive, given the state’s Democratic leanings.To Rothenberg’s point: President Obama won the state of New Mexico by an even larger margin than Heinrich. It’s unlikely, then, that environmental ads and contributions are what made up that five-point margin of victory.
“I’m not doubting that they did something,” Rothenberg said of environmentalists. “If they hadn’t done anything, I think Wilson still would have lost.”