There is the Constitution. Then there are House and Senate Rules. The Constitution allows each body to change or make rules as they go along.
The Dems changed the filibuster rule in the Senate. Well within their Constitutional authority.
A lot of bitching about nothing that really matters.
The Pubs can keep that rule alive if and when they regain the Senate. Then watch the Chuck Schumers of the Left howl and scream foul.
Just one more compelling reason to repeal the 17th Amendment. Federalism means shared power with the States. Senators were originally intended to represent State Legislatures, not voters at large.
17th amendment was probably the worst or the 2nd worst amendment of all time.