(Olympia, WA)  --  Washington voters will decide in November on whether to approve the nation's first carbon tax.  Supporters of Initiative 732 say it would help the state cut greenhouse gas emissions and could set the tone for a national policy on climate change.  The "Spokesman-Review" reports I-732 has failed to gain support from some of the groups that would typically back efforts to cut down on carbon emissions, including the Washington State Democratic Party and the Sierra Club.  Business and labor groups also oppose the initiative.