It started with the decision in Bush v. Gore to end the 2000 Florida recounts. It was decided strictly based on which party appointed the justices. It was a very poor decision and cast doubt on the election.
In 2013, he Senate Democrats under Harry Reid eliminated the 60 vote threshold for justices except for the Supreme Court. I think he had to do this because Republicans were blocking Obama’s nominees. If he hadn’t, Trump would have even more judicial openings. Republicans stole a Supreme Court seat from Obama and I will never forgive them. This has really politicized the process.
Now that Republicans are in charge, they have eliminated the “blue slip” tradition.
They eliminated the threshold for Supreme Courts justices. They are picking extreme conservatives (Gorsuch and Kavanaugh). If there is a vacancy in the last year of Trump’s presidency (2020), it would be extremely wrong and hypocritical if Republicans tried to fill it.
At some point in the future, Democrats will have a chance to select Supreme Court justices. Their base will demand that they pick extreme liberals.
30 or 40 years from now, the Court will be all extreme liberals and conservatives and there will be no moderates or compromises. Every decision will be along party lines. You can thank the Republicans for this.
It’s obvious today that Kavanaugh can’t be fair.