Most projects for the 2021 Senate composition will have both parties at 50 +/-2. Democrats are likely to lose one seat (Alabama) and Republicans are playing defense in several seats where early fundraising and favorability polling supports plausible Democratic pick-up in Arizona, Colorado and Maine. There are several other seats up for grabs right now.
There is a thin chance of a 59 seat Republican Senate, and a chance of a 47 seat Republican Senate. There is no chance of a 60 seat Democratic Senate in January 2021. Plausible policy pathways for Democratic preferences are constrained by whatever can go through a 51 vote procedure. This means either getting rid of the filibuster for legislation and equalizing legislation with confirmation standards, or reconciliation.
Sinema is a NO on getting rid of the filibuster
“They will not get my vote … whether I’m in the majority or the minority I would always vote to reinstate the protections for the minority” https://t.co/b2ekoUz66i
— Bill Scher (@billscher) October 29, 2019
Health policy that can go through reconciliation with fifty votes and a friendly Vice President means that we would be living in a world controlled by Senator Murkowski (R-Alaska) or Senator Manchin (D-West Virginia). Those are the senators who are likely to defect from their majority caucus position. This realization should strongly inform what is mechanically plausible after a Byrd Bath. It should also inform to a somewhat lesser degree what is politically possible.