President Barack Obama delivers remarks at General Motors Auto Plant in Hamtramck, Mich., July 30, 2010.

President Barack Obama delivers remarks at General Motors Auto Plant in Hamtramck, Mich., July 30, 2010.

President Barack Obama signs the hood of a Chevy Volt, during a tour of the General Motors Auto Plant in Hamtramck, Mich., July 30, 2010.

President Barack Obama signs the hood of a Chevy Volt, during a tour of the General Motors Auto Plant in Hamtramck, Mich., July 30, 2010.

President Barack Obama, with Assembly Manager Teri Quigley, drives a new Chevy Volt, during his tour of the General Motors Auto Plant in Hamtramck, Mich., July 30, 2010.

President Barack Obama, with Assembly Manager Teri Quigley, drives a new Chevy Volt, during his tour of the General Motors Auto Plant in Hamtramck, Mich., July 30, 2010.