Obama Would Have Evolved On His Own?

That's what John Dickerson is hearing:

White House and campaign officials have been talking about it for months. According to several sources involved in the campaign, the president was going to make his announcement soon, before the convention (and maybe even very soon) if for no other reason than to avoid a fight over the party platform and to rally gay supporters. Biden stepped on his plan, making it look like the president was backing into a decision and controlled by events.