Senate sponsors of a major global warming bill lowered expectations yesterday on their chances for final passage as aides scrambled behind the scenes to complete a revamped version of the legislation before next month's scheduled floor debate.

Environment and Public Works Chairwoman Barbara Boxer (D-Calif.) shrugged off suggestions she is having trouble winning over moderates and conservatives from either party in her quest to find 60 votes and squash an inevitable filibuster.

"To tell you the truth, we don't know if we'll wind up getting 60 votes this time," Boxer said in an interview. "But we do believe we're making tremendous progress and we're going to start the debate."

Sen. Frank Lautenberg (D-N.J.), who provided a critical swing vote for the climate bill last winter when it moved out of the EPW Committee, provided a similar assessment. "I don't think we can count on 60 at this point," he said.

Aides to Boxer and Sens. Joe Lieberman (I-Conn.) and John Warner (R-Va.) have been working over the last few weeks on a substitute to their original climate bill with several changes compared to the version adopted in committee last December. Lieberman said he expected the manager's amendment would get wider circulation Monday, with a public rollout shortly after.

"The whole idea is to get a draft out to our colleagues, to stakeholders, and we presume, to the public to see what we're thinking," Lieberman said. "And then invite responses so we can continue to improve it."

Warner yesterday said he was looking for changes before the floor debate that would allow the president to "pull back the throttle" if the legislation's emission targets cannot be met with available technology, or if the U.S. economy was under stress through, for example, $5 a gallon gasoline.

Boxer has also promised several changes to the bill, including a "deficit reduction" amendment, as well as greater oversight of the carbon markets and specific funding directed toward cities to help promote energy efficiency and mass transit.

Many demands

The Lieberman-Warner-Boxer camp is facing increasing demands from all corners of the Senate to change the bill that would establish a cap-and-trade system with midcentury emission limits of 70 percent below 2005 levels.

Ohio Democratic Sen. Sherrod Brown told the Cleveland Plain Dealer this week he was holding out in his support for the Lieberman-Warner bill because it did not do enough to protect his home state's manufacturing jobs while still stimulating investments in alternative energy. "I have serious concerns about any climate-change bill that doesn't take into account energy-intensive industries like we have in Ohio -- glass and chemicals and steel and aluminum and foundries," Brown said.

"He's concerned," Brown spokeswoman Joanna Kuebler explained yesterday. "He's leaning toward a no."

Sen. Maria Cantwell of Washington said in an interview that she is also pushing for changes in the Lieberman-Warner bill to benefit her home state's abundant supplies of hydropower. "We want to make sure people who are already good at reducing CO2 emissions will continue to do that and not be penalized," she said. Cantwell explained that she has not joined the bill as a cosponsor because she wants to keep working on it.

Sen. Kent Conrad (D-N.D.) said he wants a more beneficial emission allocation system for his state's rural energy producers.

"Obviously, I represent a state that's a significant power producer," Conrad said. "Most people don't think of North Dakota that way. But we produce electricity for nine states. We have the largest coal gasification plant in the country. We have very large reserves of lignite coal."

In contrast, Sen. Ben Nelson (D-Neb.) maintained that he is a long way from backing the Lieberman-Warner bill. Instead, he is taking a close look at an alternative climate bill circulated from Sen. George Voinovich (R-Ohio) that opens with tax incentives for new energy technologies but falls back on cap and trade if the other ideas have not worked by 2030.

"It's a more realistic approach to what technology is going to be required," Nelson said. "Just legislating it doesn't get you there."

(Note to Nelson: Nooooo!)

On the Republican side of the aisle, Sen. John McCain of Arizona plans a major climate-themed speech Monday in Portland, Ore., that his aides say will spell out in greater detail what he hopes to do on the issue if elected president this November. McCain will cover issues relevant to the Lieberman-Warner floor debate, including how to limit costs to the U.S. economy and also how to safeguard U.S. manufacturers concerned about international competition, an aide said.

Back in Washington, Sen. Judd Gregg (R-N.H.) spoke on the Senate floor yesterday on a different method for using what are projected to be hundreds of billions of dollars in revenue raised through an auction of emission credits. Gregg suggested the auction revenue could go toward reducing personal income taxes, as opposed to its current function with Lieberman-Warner, which ranges from research and development of new energy technologies to helping low-income energy consumers.

"This should not be a windfall that expands the size of federal government," Gregg said. "It's not right to do that."

This post was created for ClimateProgress.org, a project of the Center for American Progress Action Fund.