Democrats in the Senate are trying to make progress on a climate change bill to give a boost to an international global warming summit in Copenhagen in December.
A key Senate committee holds high-profile hearings this week, but passage by the full Senate was unlikely this year.
Passage, this year or next, will depend partly on conflicting pressures lawmakers face in their home states. Attracting support from moderate Democrats, along with at least a few centrist Republicans, in some of those states is considered essential.
Here is a look at some of the main issues and players:
WEST VIRGINIA -- KING COAL
First discovered in the state in 1742, coal is buried in 53 of the state's 55 counties and contributes directly to about 40,000 jobs. About 14 percent of U.S. coal production comes from West Virginia, ranking it second behind Wyoming.
So it's no surprise that Democratic Senators Robert Byrd and Jay Rockefeller want to make sure any climate bill passed by the Senate does not move too fast in mandating reductions in carbon emissions from dirty coal-burning utilities and factories.
Rockefeller denounced the bill when it was outlined by fellow Democrats John Kerry and Barbara Boxer on September 30. He wants to make sure there is more time for clean coal technology to be developed before emission-reduction targets start to bite.
ARKANSAS -- POVERTY AND DUCKS
Switching from cheap fossil fuels to more expensive wind, solar and other alternative energies likely would raise consumer prices.
Senators representing poor states fear such increases, even small ones. Democratic Senators Blanche Lincoln and Mark Pryor worry that a climate change bill could hurt rice and soybean farmers and others in Arkansas, which ranks fourth in the country in poverty.
Lincoln chairs the Senate Agriculture Committee, which also will review the climate bill.
But sometimes it is life's personal experiences that influence a senator's vote.
In testimony to a Senate panel in January 2007, Lincoln noted her past opposition to a climate bill but had come to believe that we must take action to control global warming.
One reason: She comes from a family of duck hunters and the birds might stop migrating as far south as Arkansas because of warmer temperatures in some Northern states. That, she said, could have a devastating impact on Arkansas' sportsmen and local economies.
Recently, Lincoln has been talking about a more limited approach to climate change for now -- passage of just an alternative energy bill that many of her colleagues worry would be insufficient in the climate fight.
MONTANA -- COAL, WIND AND GLACIERS
Montana holds some of the largest coal reserves in the world and is the fifth-largest U.S. producer of the polluting fuel. Climate change legislation aims to phase out coal-burning utilities and factories unless cleaner methods are set.
Montana also has potential for wind and other alternative energy production that a climate bill would boost. Meanwhile, the glaciers in Glacier National Park, a major tourist attraction in Montana, have been receding rapidly and could disappear by 2030, according to government estimates.
Against that backdrop, Democratic Senator Max Baucus will play a major role in any climate change bill as chairman of the powerful Senate Finance Committee. The panel has a say over whether trade protections for U.S. industry are inserted into the bill. It also will have input on the sale versus giveaway of carbon pollution permits to companies.
In the words of one global warming expert: Alaska is melting and she knows it. That she is Alaska Senator Lisa Murkowski, the senior Republican on the Senate Energy and Natural Resources Committee.
The state is seeing significant loss in mass of two major glaciers and some coastal towns could be overwhelmed by flooding. Ocean acidification related to carbon pollution threatens fish populations.
But Alaska is also one of the leading oil-producing states. While she hasn't closed the door to voting for a Democratic bill, Murkowski is demanding it contain a significant expansion of offshore oil drilling and nuclear energy.
INDIANA -- COAL AND CORN
In calculating a winning strategy, backers of climate legislation often muse over Indiana, where Democratic Senator Evan Bayh and Republican Senator Richard Lugar are well aware that more than 90 percent of the electricity generated in their state comes from coal.
Agriculture is also an important industry, with Indiana being a major corn and soybean producer. While the farm community fears the climate bill would make for more expensive fuel and fertilizer, some fear global warming in the long term will bring more violent storms that could hurt crops.
Lugar, a foreign policy expert, noted in an August 29 speech that global warming could lead to conflict and instability in countries suffering worsening drought, famine and disease.
THE STATE OF MCCAIN
Arizona Senator John McCain's upcoming role is a big question mark. As the Republican nominee for president in 2008, he is one of the more influential voices in his party. That is especially true here, as McCain was far ahead of most by calling for action years ago to battle global warming.
But he has dismissed the climate bill that passed the House and the one pending in the Senate.
McCain, whose state is home to Palo Verde, one of the largest U.S. nuclear power plants, wants a climate bill to include incentives for building more nuclear plants, beyond aid the industry already gets. He says the Democrats' bill falls far short.
(Reporting by Richard Cowan in Washington; Editing by Eric Walsh)