Greentech Media

JOHN MCCAIN: McCain has said that curbing global warming will be a central issue of his presidency, and he is the most direct among Republicans in tying climate change to greenhouse-gas emissions.

He co-sponsored an early climate-change bill that included the first mandatory greenhouse-gas reductions. Now, however, that bill is more modest than others floating around Congress. A big chunk of the money raised in a carbon auction would go toward nuclear power.

He wants the federal government to pay for a national challenge to come up with more advanced car batteries, and wants to use his office to promote partnerships between utilities and automakers to accelerate the deployment of plug-in hybrid cars.

McCain, famously suspicious of ethanol as an alternative energy source, changed that position as he was campaigning in Iowa this year. He says that sugar cane, switchgrass and corn-based ethanol may be necessary alternatives to oil now that gas prices have risen so high, and that ethanol can help cut down on greenhouse-gas emissions.

However, McCain opposes government subsidies for ethanol, solar, wind and what he considers other "mature" industries, but says he would support government-funded research in coal gasification and some hydrogen-related technologies.

Cleantech donors: Vinod Khosla, Khosla Ventures: $2,300

Car: Cadillac CTS - 20mpg

League of Conservation Voters score: 26/100