He said in 2012 that he told Obama “don’t go” without more info. In 2015, he started saying he’d said “go.”
A look at what he’s said and what others have said: cnn.com/2020/01/04/pol…
In Biden's 2015 account, he'd said he'd never give Obama a firm opinion at a group meeting, so waited, and said "go" in private.