GLOBAL WARMING

McCAIN supports a cap-and-trade system to reduce pollution from industrial greenhouse gases. However, he would find himself at odds with business groups and some conservatives who are cool to climate change legislation.

OBAMA wants the U.S. to play the lead role in global talks on a new climate change agreement to replace the Kyoto Protocol, which the U.S. has not ratified. Like McCain, he favors a national cap-and-trade system for domestic industry to reduce emissions of greenhouse gases.