It's definitely a full frame dSLR camera, like a Canon 1Ds or 5D, or Nikon D3 or D700. With the focusing issues on the 1D MkIII, along with significant price rebates from Nikon, a lot of news services have adopted the D3.
It's a slight wide angle, like a 35mm or 28mm. You don't see a lot fixed length lenses on the campagne trail, so my guess would be either the 28-70mm, or 24-70mm lens, shot wide open. This really shows how great these new cameras are in low light situations.
No way at all this was shot with a point and shoot.
Digitally manipulating the DOF in a news photo would be strictly forbidden.
Maybe they'll get Obama to be the cool guy on the new Mac ads?
David Buzzard