I don't get what broken rules or "double standards" everyone is panicking about here. It's just the new norm is that Supreme Court nominees, from now on, won't get confirmed with the opposition party in the Senate. Not the same as court packing and not going to lead to end of democracy either.
Yes.
https://www.politico.com/story/2007/07/schumer-to-fight-new-bush-high-court-picks-005146New York Sen. Charles E. Schumer, a powerful member of the Democratic leadership, said Friday the Senate should not confirm another U.S. Supreme Court nominee under President Bush “except in extraordinary circumstances.”
Obviously this feud goes quite a while back but this isn't a particularly major change of precedent. Its still a bad statement arguably although its understandable that both parties see SCOTUS as very paramount and important. I will say Mitch's turnaround from 16 > 20 was absurd. The smarter move for Mitch to have done back in 2016 was demand a moderate conservative like Hardeman which Obama would not have wanted .