“R’s should press the Supremes to weigh in on this.”
They will threaten and promise but I really doubt they will. They have now set a pretty solid pattern.
“If they hear it, it’s likely they will reflexively reply the Constitution permits the Senate to make its own rules.”
Or they will rule that “in this particular case” the Senate was right. They keep coming up with “yes but no” rulings that renders themselves immune from discretion and doesn’t actually settle anything.
“If they hear it, it’s likely they will reflexively reply the Constitution permits the Senate to make its own rules.”
That is what the Constitution says, whether we like it or not.