Since Robert Mueller was appointed special counsel 16 months ago, his investigation has endured an unrelenting onslaught of attacks from the president and his allies. But Friday morning provided the latest, strongest evidence that the probe has not been hindered. President Donald Trump’s former campaign chairman Paul Manafort announced a deal with the special counsel’s team Friday morning, pleading guilty to two criminal charges and agreeing to cooperate with the investigation. The plea was all the more stunning for the fact that Manafort is the fifth Trump aide to plead guilty in connection to the special counsel’s probe.