WASHINGTON -- In an election all about change, environmental groups are doing the usual -- endorsing the Democratic presidential candidate.

The League of Conservation Voters will become the latest green group to back Democrat Barack Obama in six separate events across the country Monday. Its pick shouldn't be a surprise. Its scorecard of votes on environmental issues for the first session of the current Congress gave Obama a score of 67 and Republican John McCain a zero. The Arizona senator did not show up for any of the votes the group scored.

"When you look specifically at the twin challenges of cutting global warming pollution and moving toward a clean energy future, on those issues Barack Obama has the most comprehensive plan we have ever seen for a presidential nominee," said league president Gene Karpinski. The league has endorsed presidential candidates since the early 1980s, but not once has it selected a Republican.

Obama thanked the group in a statement, saying that "together, we will create a better, cleaner, more secure future."

Friends of the Earth and the Sierra Club announced their support for Obama earlier this year, citing McCain's support for more offshore drilling, expanding nuclear power and a gas tax holiday.

Neither group has ever backed a Republican presidential candidate, although in 1988 Sierra Club made no choice because both Republican George H.W. Bush and Democrat Michael Dukakis would have been good stewards of the environment, said spokesman Josh Dorner.

Defenders of Wildlife Action Fund, which has yet to announce its endorsement, said McCain's renegade image as a Republican crusader on global warming doesn't square with his record.

"McCain's campaign record notwithstanding, his record on the environment is decidedly mixed compared to Barack Obama's," said William Lutz, a senior director with the group.