Carrying signs with slogans like "Fight Climate Change Now" and "We Can't Wait for Climate Action," members of the coalition 1Sky already have rallied outside the regional offices of 10 senators and seven House members. They plan to visit at least three more senators' offices this week.

Calling their effort "the storm," 1Sky protesters don rain gear to symbolize weather changes that scientists predict climate change will bring.

The Sierra Club, meanwhile, is targeting about 40 House members with phone calls and office visits. The environmental group is urging lawmakers not to support any of the House measures that would restrict EPA's authority under the Clean Air Act. Moveon.org is using calls and faxes to urge Sen. John Kerry (D-Mass.) as he crafts a new climate bill not to include language that would hobble EPA's authority over carbon emissions.

The moves come as lobbyists for utilities, refineries and large businesses press lawmakers and their aides to back legislation and climate bill language that would block EPA. It is a top goal for many industries. At the same time, legislators in 17 states have introduced measures that would block or limit EPA's authority to regulate greenhouse gases. Five of those bills came from Democrats.

"The question of EPA regulating is extremely significant," said Sam Thernstrom, who worked at President George W. Bush's White House Council on Environmental Quality and now is a fellow at the American Enterprise Institute.

"The Clean Air Act gives EPA the power to impose very expensive, burdensome and highly inefficient regulations upon American businesses and consumers," Thernstrom added.

EPA in December released a finding that greenhouse gases endanger human health and welfare, a determination that opens the door for rules aimed at slashing emissions from a broad range of sources. EPA has indicated it will target the largest sources, with EPA Administrator Lisa Jackson saying the agency plans to begin regulating some big stationary facilities in January 2011 when automakers must start complying with EPA's new rules for tailpipe emissions.

There are multiple measures in Congress to stop EPA. Legislation from Sen. Lisa Murkowski (R-Alaska) that would veto EPA's endangerment finding has 41 Senate co-sponsors, including three moderate Democrats. The resolution would need 51 votes to clear the chamber. There are multiple companion bills in the House with Democratic sponsors.

And Kerry and his fellow senators who are crafting a new climate bill are considering language that would bar EPA from regulating greenhouse gases. Language stripping EPA of its power is needed in the bill to gain support from moderate Democrats and Republicans, Sen. Joe Lieberman (I-Conn.) has said. He is working on that bill with Kerry and Sen. Lindsey Graham (R-S.C.).

Stopping those measures and protecting the Clean Air Act is a top goal of 1Sky, said Alex Posorske, the coalition's field and communications manager. The coalition includes environmental groups, businesses, religious groups, health organizations, social justice and military leaders, and others.

"It's a critical tool especially if a climate bill doesn't go through," Posorske said of the Clean Air Act. The act, he said, "is something for the administration to use in cracking down on coal plants that are responsible for some of the greatest emissions."

As senators craft a new climate bill, so many concessions are being made for conservatives that the measure is hemorrhaging support from progressive Democrats, said Steven Biel, Moveon.org's campaign director. After Kerry told E&E he would consider trading EPA's Clean Air Act authority for a carbon cap, Moveon.org polled members on whether they would support such a climate bill. The survey found that 64 percent of members would "definitely oppose" and 23.3 percent would "probably oppose," Biel said.

If the group's 5 million members do not rally behind climate legislation with calls, e-mails and letters to moderate Democrats, Biel said, those key lawmakers won't feel the need to back the bill.

"You get Senator [Claire] McCaskill by having her feel from her constituents that she needs to be with the bill politically," Biel said, referring to the Democratic senator from Missouri.

The Sierra Club's new executive director, Michael Brune, told the Los Angeles Times last week that the group would oppose climate legislation that revoked EPA's ability to regulate greenhouse gases.

Natural Resources Defense Council has also said that it wants to protect EPA's authority under the Clean Air Act and that it urges the Senate not to include language in a climate bill that would strip EPA's power. It won't say whether it would oppose a climate bill that blocked the agency from regulating greenhouse gas emissions. Detailing provisions that would cause NRDC to oppose a bill would give opponents "a blueprint of how to try to block a bill," said David Hawkins, director of NRDC's Climate Center.

Fighting to keep EPA authority and also pass a comprehensive climate bill is a big request, Thernstrom said.

"The threat of EPA regulations is a potentially useful bargaining chip for environmental advocates who are trying to influence swing voters in Congress," Thernstrom said.

"The real challenge of climate change is to be able to govern from the center, something that is going to be politically popular with the voters and therefore sustainable for generations," Thernstrom added.

Targeting moderates

So far, 1Sky coalition members have visited the local offices of McCaskill, Kerry, Sens. Michael Bennet (D-Colo.), Blanche Lincoln (D-Ark.), Lindsey Graham (R-S.C.), Scott Brown (R-Mass.) Mark Pryor (D-Ark.), Susan Collins (R-Maine) and Olympia Snowe (R-Maine), and Senate Majority Leader Harry Reid (D-Nev.) The activists plan this week to stop at the offices of Sens. Arlen Specter (D-Pa.), Byron Dorgan (D-N.D.) and Judd Gregg (R-N.H.).

Between 40 and 70 alliance members have participated in each of the events, Posorske said. The group picked the lawmakers because they are seen as moderates or otherwise central to protecting EPA's powers, Posorske said.

So far Bennet is the only senator to commit to backing EPA and the Clean Air Act, Posorske said.

"The Clean Air Act is one of our nation's strongest and most effective pieces of legislation, and for 40 years we have seen that protecting the air we breathe does not have to come at a cost to the national economy -- both can improve hand-in-hand," a Bennet spokesman said in an e-mail. "The Clean Air Act has been successful in reducing dozens of different air pollutants and protecting the health and environment of millions of Americans -- particularly our most vulnerable populations."

Bennet will "strongly oppose efforts to gut the Clean Air Act," the Bennet spokesman said.

Sierra Club members are talking to House members and their aides because so much attention has been focused on the Senate with Murkowski's measure, said David Hamilton, the Sierra Club's director of global warming and energy programs. The environmental group is urging lawmakers "to defend the Clean Air Act," he said.

"This is the point at which one of our bedrock environmental acts is under attack," Hamilton said.

Industry groups, meanwhile, continue their lobbying for legislation that will yank EPA's authority under the Clean Air Act.

"Pre-emption of both overlapping EPA authority and state actions are an essential prerequisite for passing climate change legislation," said Scott Segal, a Bracewell & Giuliani lobbyist who represents coal-fired utilities and energy companies. "Without such pre-emption it's almost impossible to estimate how expensive the legislation will be because we don't know what combinations of authorities and actions will eventually be applicable."

Pressure is coming from multiple segments of the business community, Segal said.

"Every potentially regulated company that I am familiar with are asking the Congress with clarity to address EPA authority and overlapping state authorities," Segal said, adding that "pre-emption is on almost every trade association's list of issues to be addressed."

Congress does not necessarily need to block EPA if it can pressure President Obama to restrain the agency, said Charles Ebinger, director of the Energy Security Initiative at the Brookings Institution, a Washington think tank. Obama may be "willing to give up the EPA to get an energy bill," he said.

"What is more likely to happen [is] that you don't pre-empt EPA's authority but you don't exercise it," Ebinger said. "You don't move aggressively to push the EPA to enforce it. You leave it in limbo."