First, a major procedural change would create immense uncertainty for Democratic incumbents. In my conversations with current and former Senate GOP staffers, I find near unanimity in predicting one outcome: In the short term, the nuclear option would create chaos. The Senate would immediately come to look a lot more like the House, where the speaker rules with an iron fist. In a purely majoritarian Senate, the majority leader becomes the gatekeeper for lawmaking. Anything that reaches the floor of the Senate would presumably become law with relatively little deliberation, as the need to build consensus went out the window. At least in the short term, this would likely make lawmaking even more polarized than it already is.
To put this in concrete terms: Chuck Schumer, newly empowered, would have to navigate treacherous political waters with a deftness he has not, to date, shown. Likewise, individual senators would face countervailing political pressures, pressures that would pit their general-election prospects squarely against the priorities of the partisans in their primary electorates.
As the political scientist David Mayhew notes in his book Partisan Balance, the filibuster functions as a kind of “intensity net” that scuppers legislation that the majority may support mildly but that roughly a third of the chamber opposes fiercely. Senators can play both sides of this net. If a bill beloved by the base will certainly fail, they can vote for it without worrying about paying in the general election for its material consequences. Conversely, a bill doomed to failure can be an opportunity to burnish one’s bipartisan credentials by crossing the aisle without the consequence of passing policy. Manchin is the master of this strategy, always there for a bipartisan vote when it no longer matters.