Both Trump and Russia have a lot to lose if the allegations of collusion come to anything substantial.
We've all seen how Russia like to deal with people who get on the wrong side of them. Obviously, they invite them round for a nice cup of tea and have a lengthy discussion until one of them starts to foam at the mouth.
I really wouldn't be at all surprised if somebody like Robert Mueller or one of his close family members has an "accident", such as a hit-and-run, or robbery gone wrong, and Russia had the evidence that The Donald sanctioned the accident. This would put Trump firmly in the pocket of the Russians (if he isn't already).
This kind of thing probably (highly likely) went on years ago with the Kennedy's and Nixon, but living in the age we do now, it is a lot more difficult to hide stuff.