I work in government, and if the politics here is any indication of the system as a whole, I can tell you that the bureaucracy is extremely well set up to spread or shift blame. No one is responsible for anything other than their little piece of work, which is dependent on someone else's work. If you screw up, it's always the fault of 10+ other people that either didn't provide you the information in time, or didn't provide the correct information. "It's not my job" is the rule around here. So, with years of practice of shifting and diverting blame for things, I seriously doubt anyone will be finger as having sole responsibility. The most you could get out of a situation like that is someone at the top stepping down for whatever reason, even if they themselves had nothing to do with it either (though you could blame them for having a lack of oversight, as mentioned, it's impossible to see who did what here).
Again, I'd just note that this is currently a criminal investigation. That says a lot. That means it's already moved out of the "business as usual" category.
So, who went to jail when IRS targeted Martin Luther King? Or for having them audit Paula Jones under Clinton? Or when they targeted John Birch Society under Kennedy? Or the slew of political opponents under Nixon and a slew of liberal organizations and churches under G W Bush? It's as if this is a new thing.
Since this has started back in 2010, I'm going to put on my tinfoil hat and come up with a theory. What does Obama have to gain from targeting Tea Party groups? Answer is almost nothing. On the other hand, establishment Republicans have considered the Tea Party a huge threat from the start. Tea Party does populist politics and astroturfing really well, attracting common Joe Shmoe, but pick really awful, terrible candidates. Most of the Tea Party candidates that won primaries in 2010 were downright fucking nuts, and most of them didn't win, because they only appealed to the loony fringe. Republicans fought them during the primaries, and were always under a threat from the Tea Party of being primaried in otherwise safe "red states," which would divide the vote, and cause the state to turn blue (which actually happened in 2010). So, some high ranking Republican Senators and/or House members secretly instructed the IRS to target Tea Party groups, and make it as hard for them to raise money and participate in politics as possible. As a result, they were able to regain a lot of the seats they lost in the 2012 elections. And if they get caught, they can just blame it on Obama, since it would be "obvious" to everyone that he is the "Scary Black Man™ who is only in office because he cheated, and he is the only one with incentive to attack Tea Party I mean Republicans."
I'm sure that's not what happened, because I doubt politicians are smart enough to think up of something like that, but this theory would make much more sense than Obama wanting to target the Republican's third party black sheep himself. Of course, major political parties NEVER screw with politics by attacking their own fringe or supporting the fringe of their opponents. Except that time Democrats attacked the Green party and Republicans ran adds supporting them in every election...