The Sierra Club and the League of Conservation Voters, two key environmental groups who have previously endorsed Rep. Mark Kirk, will announce today they are supporting Alexi Giannoulias in the general election for U.S. Senate in Illinois. The organizations, which hinted that they might dump Kirk last December, cited his cap-and-trade flip-flop and his efforts to stop BP from polluting in Lake Michigan as the reasons for their decision.

UPDATE (1:30 P.M.): From a Sierra Club Press Release:

"Alexi Giannoulias is the best choice to represent the interest every Illinois citizen has in a healthy environment and the transition to a clean energy economy," said Jack Darin, Director of the Sierra Club, Illinois Chapter.   “As our Treasurer, Giannoulias has been a key leader in developing new environmental programs that helped clean the air and grow clean businesses, and as our Senator he will stand up to the special interests to protect the water we drink and the air we breathe.” [...]

“The BP spill in the Gulf reminds us all how critical it is that we move beyond oil and dirty energy, but Mark Kirk wants even more drilling in the Gulf of Mexico, and is against clean energy and climate legislation,” said Jack Darin.  “Alexi Giannoulias is the clear choice for Illinois voters who want to move beyond big oil to a cleaner, better energy future that creates good jobs here in our communities in the industries of the future.”