You got the cart in front of the horse. The bad verdicts (OJ, Casey Anthony, etc.) are the direct result of jury nullification. Blago's defense didn't dare attempt jury nullification, as to do so would have directly involved the President of the United States. No lawyer since John Dean has gone there...
I believe Blago’s team did try to involve members of the administration. The judge refused to allow it.
That being said, I believe the prosecutor has grounds to file charges against administration officials, but having seen how Clinton scandals turned out, probably figured it was a lost cause here.