Though David Petraeus seemed content to work for the Obama Administration there was news media speculation that he would eventually run as a Republican for president. This would likely be in 2016. The administration could have concealed the Petraeus scandal but they exposed it at a time when Petraeus appeared to question the White House Benghazi talking points. The scandal allowed Obama to remove Petraeus as a potential Benghazi critic and spike him as a future threat to a Hillary presidential run. Eric Holder has dragged out the investigation this long because it gags all the witnesses including Petraeus from publicly commenting on the case. If this story is a warning to Petraeus from the White House it is a weak and perhaps desperate gesture. It may be Petraeus has a book ready to release.
Please see 26-28.