I don't think it's payback. I think it's Clinton second term all over again. I know for a fact that I personally posted that Obama would be impeached in his second term if the Republicans controlled the House. None of this is the least bit surprising. They are throwing literally everything to the wall and seeing if anything can stick. They will spend the remainder of his term holding costly investigations, attempting to taint the administration as "scandal-plagued" until Americans figure something must be on fire what with all the smoke. Look at Jon Stewart, he has already fallen for that tactic.
They may even eventually accidently stumble onto a real scandal. Whether they do or they don't won't matter, they will try to impeach. It's coming.
It gets so tiring. This crying wolf makes the public desensitized to real scandal..