League of Conservation Voters
The League of Conservation Voters (LCV) is a United States political action committee founded in 1969 to turn "environmental values into national priorities. Despite its name, the organization actually favors environmentalism over conservation. LCV’s mission is to advocate for sound environmental policies and to elect pro-environmental candidates who will adopt and implement such policies."  They endorsed Barack Obama and congressional Democrats in 2008. Occasionally the LCV endorses liberal Republicans such as Susan Collins, Christopher Shays, Michael Castle and Mark Kirk.