No one should expect the President to know everything the NSA is doing, said Julian Zelizer, a professor of history and public affairs at Princeton University.
"But when you're talking about the surveillance of world leaders, and an issue that's been controversial for a while now, you would expect that there's some knowledge either by the President or people surrounding him. ... I do think there's surprise that this was off the radar in the inner circles of the White House."
Time for change?
Republican Rep. Peter King, a key member of the Homeland Security Committee, said if the surveillance happened without the president's knowledge, it has larger implications.
"I would say if the president did not know, that raises very serious questions about what he's doing as chief executive. The fact he would be going into negotiations and discussions and meetings with Angela Merkel or French leaders -- or any leaders for that matter -- and not be aware that there was surveillance going on of the private phone calls, to me either something is definitely wrong in his administration or he just has a totally hands-off attitude. To me, this is unacceptable."
Ross Douthat, a CNN political commentator and a columnist for The New York Times, wondered whether some officials would lose their jobs if the president really wasn't informed.
"The question becomes, why do the people who failed to keep him in the loop still have their jobs?" he asked.
No matter what Obama knew, or when, some say it's time for a new approach.
"He has often said that he didn't know what was going on with the (HealthCare.gov) website. ... He can't pretend he doesn't know and walk away from problems anymore, because he has been caught too many times out of the loop," said A.B. Stoddard, associate editor of The Hill. "He can't do his job that way."