That is a Boeing C-32 (757 variant).
http://en.wikipedia.org/wiki/Boeing_C-32
I think one of the airports he visited cannot handle a VC-25 (747) of which there are two that typically serve as AF1.
http://en.wikipedia.org/wiki/Boeing_VC-25
See also:
http://time.com/3550255/obama-campai...the-spotlight/