I recently finished the fascinating Seymour Hersh memoir, Reporter (I highly recommend it!). In the book, he makes clear that early on he was not focused on Watergate but that eventually changed. And then a White House aide, Egil Krogh, who knew what was going on spilled the beans to Hersh that he was part of a Nixon dirty works operation, the Plumbers.
I was stunned by what he told me...After my hour or two with him...I knew that the emerging Watergate scandal was going to get much darker, as did Bud Krogh. He subsequently agreed to cooperate with Federal prosecutors...It strikes me that Micahel Cohen who was Trump's fixer for 10 years could have game-changing information the way Krogh had. Up until now, I did not see the Trump getting seriously damaged by the Mueller investigation, but if anyone can do it, it is Cohen.