Duke Energy has left the American Coalition for Clear Coal Electricity due to policy differences over global warming legislation. These alliances have grown shaky lately. Here's a clip from Amy Harder's story at NationalJournal.com:

As the Senate prepares to return to Washington and resume its debate over climate change legislation, energy companies are walking a fine line. Many have dual membership in groups on opposing sides of the issue, and their attempts to play both sides are becoming increasingly apparent -- and potentially damaging to the companies and the coalitions alike.

General Electric, Alstom Power and Caterpillar are members of both the American Coalition for Clean Coal Electricity and the U.S. Climate Action Partnership. The former is a pro-coal group that opposed the recent House energy legislation, and the latter is an industry-environmentalist coalition whose recommendations provided much of the basis for the that bill, which passed the House by a vote of 219-212 in June. On a similar note, ConocoPhillips, Siemens and BP America are members of both the American Petroleum Institute (which opposed the bill) and USCAP.

These dual memberships shouldn't be surprising but could be problematic if they become more common, according to Burdett Loomis, a lobbying expert who teaches political science at the University of Kansas. "It seems to always be a mix of motivations," Loomis said. "And, as coalitions have become increasingly important on all sides of the issue, it's not surprising that there are some real or perceived conflicts."

You can read the full story here.