[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/images/08/21/art.boselection0821.ap.jpg caption="While making the rounds in Virginia Thursday, Sen. Obama told reporters that he'd decided on a running mate but refused to say any more."]
(CNN) - The VP choice was a difficult one for Obama, a source close to the Illinois senator tells CNN's Gloria Borger.
Specifically Obama was "very hung up on the experience versus change,” the source said, and how his message of change may conflict with a longtime Washington insider.
The source doesn't know who Obama ultimately chose, but confirms Sens. Joe Biden and Evan Bayh, along with Virginia Gov. Tim Kaine are all in the running.