Special Counsel Robert Mueller stepped down Wednesday saying the work of his team is done.  And while partisans on all sides latched on to different comments from Mueller's statement, former federal prosecutor Andrew C. McCarthy says Democrats got everything they could have reasonably hoped for.

President Trump and his allies exulted that Mueller repeatedly insisted the report he issued in April serves as his full testimony and that he didn't want to distract from that.  But Democrats are seizing on two parts of the statement as fuel for impeachment - both related to Mueller's refusal to exonerate or indict Trump for obstruction of justice.

"If we had had confidence that the president clearly did not commit a crime, we would have said so," said Mueller.

Mueller further stated that he was constitutionally barred from indicting Trump due to a long-established policy from the Justice Department's Office of Legal Counsel, or OLC .

"It explains that under longstanding department policy , a president cannot be charged with a federal crime while he is in office.  That is unconstitutional," said Mueller.

Mueller's pronouncement that OLC policy precludes him from charging Trump flies in the face of testimony from Attorney General William Barr, who stated that Mueller told him and then-Deputy Attorney General Rod Rosenstein that he was not relying on the OLC precedent in refusing to make a decision on obstruction charges.

McCarthy, who served as Chief Assistant U.S. Attorney for the Southern District of New York, says both men may be telling the truth.  He says Barr is referring to a March meeting with Mueller that took place weeks before the Mueller report was submitted to the Justice Department.

"It was at that meeting that Mueller first alerted the attorney general, the deputy attorney general and others that he was not going to make a decision on obstruction.  I think it was at that point that Barr asked him - and he said that Mueller was emphatic on this - whether the OLC guidance was the rationale for not making a decision and Mueller evidently said no, that that was not the reason," said McCarthy, who suspects Mueller changed his mind on the basis for the rationale during the intervening weeks.

Nonetheless, McCarthy says House Democrats now have more ammunition to push further down the road to impeachment, even though key leaders are not calling for that yet.

"He doesn't want to testify, but he did give Democrats as much as they could hope for from his testimony, I think, by saying, 'If I thought there was no crime here, I would've said so,' and it's up to you Democrats who run Congress to decide what to do about it," said McCarthy.

Listen to the full podcast to hear McCarthy's fascinating dissection of how Mueller and Barr appear to differ on what is required for a president to obstruct justice, whether Trump's worst impulses are criminal even if his subordinates did not obey him, and much more.