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“If there’s not some verifiable way to include the developing world, particularly China and India, then we’ll go through all these changes and not offset global warming substantially,” he said.

On the so-called “smart” power grid, Republicans and Democrats are largely united in support, yet some Republicans are skeptical about efforts to limit the new transmission lines’ use to renewable energy.

Republican lawmakers are joining some Democrats in opposing an effort led by Senate Majority Leader Harry Reid, Nevada Democrat, to give the federal government the power to force localities to make room for the new lines, an idea that has angered several states.

Still, a consensus is growing among lawmakers in both parties that extra money should be allocated to help “clean coal” technology, which captures and buries carbon dioxide from power plants. Democrats from the Plains states and industrial Midwest, where mining and coal-fired electricity predominate, worry that a renewable energy mandate on utilities, combined with the cap-and-trade system, will damage their economies.

Rep. Rick Boucher, a Democrat from coal-rich Southwestern Virginia who chairs a key House Energy and Commerce subcommittee, wants to spend $10 billion to develop “coal capture” technology, an idea likely to make it into Mr. Waxman’s bill.

Joe Lucas, a spokesman for the American Coalition for Clean Coal Electricity, said Mr. Bingaman still might win backing for a renewables mandate, called a “renewable portfolio standard,” but only if it contains enough flexibility for coal-dependent utilities and more money for “clean coal.”

“If a renewable standard gives utilities the right tool kit to meet the standard, then people are going to go for that,” he said.

Environmentalists see the best opportunity in years to advance both renewable energy and climate-change legislation.

“We’re very optimistic about a renewable energy standard being adopted this year,” said Jim Presswood, an energy analyst at the Natural Resources Defense Council.

But the timing of major new legislation remains uncertain. Mr. Waxman does not foresee passing his bill until Memorial Day at the earliest, and the final word from Congress may not come until next year. In the Senate, the cap-and-trade system will not even be considered by Environment and Public Works Committee until late this year or early next year.