Here, I am talking about Republican hardball, not Democratic hardball.
What if the Republican majority one day purported to amend the rules by mere majority vote to abolish the filibuster and, the parliamentarian upheld the ruling (a partisan appointment serving at will after all)?
I don't think that the U.S. Supreme Court would intervene. Article I, Section 5 of the Constitution provides that:
Each house shall be the Judge of the elections, Returns and Qualifications of its own Members, and a Majority of each shall constitute a Quorum to do Business . . . Each House may determine the Rules of its Proceedings . . . .
I think the U.S. Supreme Court would uphold a majority of those present when a majority quorum was present repealing the rule.
I'm not sure that your average Joe would be that phased by a de facto constitutional amendment through an amendment of Senate rules in violation of the Senate rules. Republican talking heads would be put on the air and the press wouldn't take sides between those opposed and those in favor. A case would be commenced and lose. The Republicans wouldn't care. While people would hate the Senate, they would still love their individual Republican Senator.
Am I wrong? Do you doubt that the Republicans might "go nuclear" and illegally abolish the filibuster in this way if they found an issue they cared enough about?