Early in 2007, a coalition of big companies broke ranks with corporate America and declared that global warming was a real, grave threat.

The United States Climate Action Partnership changed the national debate over warming. Executives from member companies such as DuPont, Ford Motor Co. and PG&E Corp. lobbied Congress to do something about greenhouse gases.

They joined forces with environmental groups that also were part of the partnership, groups such as the Environmental Defense Fund and the Natural Resources Defense Council. Together, they helped lay the groundwork for the climate bill that the U.S. Senate will debate this fall.

But now this groundbreaking partnership may have been undercut by some of its own members.