It's simple. Republicans make up shit and then the investigate the rumours they created - trying to prove Democrats did the stuff they made up. When no evidence is found, Republicans then claim that Democrats "got away with it again".
Democrats wait until Republicans DO something, and then they investigate REAL things that have happened.
In reality, Republicans seem to be indifferent to their own corruption, or alternatively, they are accusing Democrats of doing the same things that they are doing. Since Reagan was elected in 1980, Republicans have been lying to the American people.
In particular, Trump has a habit of accusing others of doing the things that he's doing. It both distracts from his own crimes, and it puts his target on the defensive. Like accusing Clinton of getting help from the Russians, when in fact, he was getting help from the Russians.