For Some, Hagel Departure Doesn't Pass Sniff Test

The White House says the resignation of Defense Secretary Chuck Hagel is a "mutual decision."

"Last month, Chuck came to me to discuss the final quarter of my presidency and determined that having guided the department through this transition, it was an appropriate time for him to complete his service," President Barack Obama said Monday.

Already leaks from White House are intimating that the 68-year-old wasn't up for the job. But many believe that Hagel, like the previous secretaries of defense -- Robert Gates and Leon Panetta -- couldn't work with the president's very tight inner circle.

"Inevitably when someone like him comes into an administration that's fairly well established, you have a number of people who have advised President Obama for a long time going back to when he was a senator," Christopher Preble, vice president for defense and foreign policy studies at the Cato Institute, said.

"In contrast, Barack Obama and Chuck Hagel's interactions with one another were fairly minimal when they were in the Senate, and so I think it's hard for an outsider to break into that inner circle," Preble said.

Hagel's resignation comes in the midst of several foreign policy crises, including the rise of the Islamic State.

The defense secretary appeared to disagree with the Obama administration's portrayal of the terror organization, with Hagel saying ISIS is the greatest threat in the Middle East, while Obama brushed the group aside, calling it the 'JV' team.

"ISIL may not appear to be an imminent threat to the United States. It is a threat to the United States. It is a threat, a clear threat to our partners in that area, and it is imminent," Defense Secretary Chuck Hagel said.

Key lawmakers say that as Obama sees his policies failing, he's looking for a scapegoat.

"Ultimately, the president needs to realize that the real source of his current failures on national security more often lie with his administration's misguided polices and the role played by his White House in devising and implementing them," Sen. John McCain, R-Ariz., said in a statement.

Now the question is who replaces Hagel?

Speculation points to Michele Flournoy, a former undersecretary of defense, as the leading candidate.

Some other possibilities include Ashton Carter, a former deputy secretary of defense, or retiring Democratic Sen. Carl Levin of Michigan, the outgoing chairman of the Armed Services Committee.

No matter who the president nominates, it's certain the new Republican Senate will not only review the nominee's resume, but also closely scrutinize the policies of the Obama administration on ISIS terrorism and other threats as well.