By Deborah Zabarenko, Environment Correspondent

WASHINGTON (Reuters) - Who's best equipped to turn the White House green -- John McCain or Barack Obama? Both have made energy security and environmental stewardship part of their presidential campaigns.

Both favor curbing the greenhouse gas emissions that spur climate change. Both say they want to stop U.S. "addiction" to imported oil.

Obama, an Illinois Democrat, has the support of most U.S. environmental groups. McCain's stance on global warming led Republicans to hope they could sway environmentally inclined independent voters.

Early in the campaign, both were seen as being an improvement over the current administration on the environment, but the difference between these two "green" candidates became more apparent after the Arizona senator advocated more drilling for oil off the U.S. coastlines and chose controversial Alaska Gov. Sarah Palin as his running mate.

"Unfortunately it's becoming more and more clear that the McCain-Palin ticket will continue the failed policies of the Bush administration and their Big Oil friends," said Gene Karpinski, president of the League of Conservation Voters, which has endorsed Obama.

Palin, who has drawn the spotlight for her distinctive "hockey mom" persona and anti-corruption moves in Alaska, favors offshore and onshore drilling for oil and gas, opposed the listing of the polar bear as threatened under the Endangered Species Act -- even though U.S. scientists found its icy Alaskan habitat was melting away -- and has questioned whether human activities spur climate change.

Jim DiPeso, policy director of Republicans for Environmental Protection, discounted what might be thought of as the Palin factor in McCain's environmental policies.

MCCAIN'S SPEAR-CARRIER