WASHINGTON -- At age 80, Bill Ruckelshaus still remembers those pro-environment days in the early 1970s, when his old Republican boss, then-President Richard Nixon, urged Americans to make peace with nature and his party joined Democrats to pass laws protecting the air and water."The public was really riled up about the health effects of pollution. Health is what gets people excited," said Ruckelshaus, of Seattle, the first administrator to lead the Environmental Protection Agency when it opened for business 42 years ago.Now, as President Barack Obama prepares to choose a new leader for the agency for his second term, any unanimity on environmental issues is long gone on Capitol Hill, where the EPA has become a favorite whipping boy for those who fear it has too much power.Whoever gets the job will face circumstances that have become familiar: criticism from the right for pushing job-killing regulations, and criticism from the left for not doing enough to crack down on polluters. And the arguments will only intensify if the president, as expected, pushes a plan to reduce emissions as a way to fight global warming.Ruckelshaus, who also headed the agency for a stint under President Ronald Reagan, said the EPA has come under attack for so long that it now suffers from "battered agency syndrome.""In some ways, it sort of frees you up to do what you thought was right," said Ruckelshaus, who wants the job to go to the former two-term governor of his state, Democrat Chris Gregoire, who left office in January. "Whatever they do, they're going to make somebody mad. And usually everybody gets mad."Gregoire, who's also rumored to be on the short list of candidates to replace Interior Secretary Ken Salazar, is one of a handful of high-profile names often mentioned as a potential successor to EPA Administrator Lisa Jackson, who announced her resignation in December.Other top contenders include: EPA Deputy Administrator Bob Perciasepe; Mary Nichols, chairwoman of the California Air Resources Board; Kathleen McGinty, a former head of Pennsylvania's Department of Environmental Protection; and Gina McCarthy, who heads air quality for the EPA.In Obama's first term, the EPA implemented standards for mercury pollution, tightened rules on soot pollution and established tougher emissions standards for new power plants. It also set higher fuel-economy standards.The administration is completing emission rules for new power plants. Environmental groups such as the Natural Resources Defense Council are calling for rules that would target existing plants.Such a move shifts the debate over regulating greenhouse gases to the executive branch and away from Congress, where polarizing politics, regional energy interests and pressure from big polluters and the influential energy sector hold more sway. Frank Maisano, a Washington-based lobbyist for energy interests, suggested someone with Jackson's social skills. Nathan Willcox, the federal global-warming program director for Environment America, backs someone who will uphold the agency's authority to regulate greenhouse gases.