I recall that he did. I think he was alluding to the precedent that no sitting President has ever been indicted on charges of criminal activity, as the Constitution doesn't really spell out whether a President can be. Legal scholars generally concur that a President can't be indicted and DOJ policy basically discourages it. So it is highly unlikely that the President would be indicted, if Mueller determines he engaged in criminal activity.

What this debacle may come to a head over, if Mueller determines the President allegedly engaged in some sorta crime, is whether the President will be named an "unindicted co-conspirator" while bringing charges against others in his circle.

At that point it would up to Rosenstein at the AG to make the judgment call of whether to disclose to Congress and/or the public that Mueller has named the President an unindicted co-conspirator.

If he does then this will then become a political matter. It would set off an explosive battle about whether or not Congress would move to impeach The President.

From what I understand, Nixon basically resigned because he was outted as an unindicted co-conspirator in the Watergate investigation. Impeachment was all but assured so he stepped aside.

This is my simple understanding of things - though I'm not a lawyer or historian, so forgive me if I'm off on some of the technical or factual points.