This one specifically that an electric vehicle would simply displace the pollution from the internal combustion engine.  Instead of getting smoke out of the tailpipe, we'd be putting smoke out the coal fired plant's smokestack.

 

And he brings numbers from Tesla motors that show it is reasonable to see an electric vehicle would do less damage per mile than a prius.

 

He also points out that the Chevy volt would have a gas generator to power the battery.

 

So the powersource to distance metric, the electric vehicle works better.