WASHINGTON — An effort to popularize plug-in hybrid vehicles got a shot in the arm from Congress when a House committee approved a bill introduced by Rep. Lloyd Doggett (D-Texas) to provide tax incentives for buyers. The measure would offer tax credits of $4,000 to $6,000 to purchasers of new plug-ins. ...The legislation would provide a tax credit of $4,000 for any plug-in vehicle. The credit could be increased by up to $2,000 for larger battery capacity. Plug-ins would not qualify for the $2,000 Clean Fuel Vehicle tax credit already available to buyers cars like the Toyota Prius, Honda Insight and other cars that have gasoline engines and electric motors operating on generator-charged batteries. Skeptics say plug-ins would harm the environment, arguing that sulfur dioxide and mercury emissions would increase with the additional burden on electric power plants. http://www.ajc.com/news/content/news/stori...0622hybrid.html