But I would caution on the idea that the other side is going to do it anyway so they have to do it first. Did the Democrats ever give indication that they would reject any nominee from a Republican president near an election? I think we've established the opposite with justice Kennedy's 97-0 approval.
The specific example that comes to my mind when I think about not playing fair is that in my view the Kavanaugh hearing was basically an attempted railroading.
Feinstein sat on the accusation for months and never turned it over to the FBI.
Many inconsistencies (Ford afraid of flying but loved scuba diving; needed second door on her house because of fear, but the door was to an illegally converted apartment she rented out; didn't remember how she got home; her own friend didn't back her up).
When story started unraveling, operatives and journalists (sometimes, the same thing), went searching for any other dirt they could possibly find, publishing it immediately with no fact checking, then often needing to walk it back quietly the next day when multiple other people contradicted it.
All purposefully done right before an election to try to derail the nomination.
I think a lot of higher up Republicans didn't want to come out forcefully saying they thought Ford was lying because they wanted to let the process work itself out, and when it became a circus, that's when the moderates mentally lost people like Lindsey Graham and Chuck Grassley, etc. From that moment, they became squarely in the "OK, then it's war" camp and what you are seeing now is the result.
But of course the whole impeachment of Clinton was a big political farce, so this has been going along for a long time in Washington. But it does seem like the stakes are getting raised every time, which is problematic for us that just want to live life in a reasonably well functioning country.