Neither Vermont or Massachusetts is going to elect a Republican to the senate. Here's the latest polls, RCP averages.
RealClearPolitics - Election 2020 - 2020 Democratic Presidential Nomination
The Northeastern progressive duo of Sanders/Warren actually has more support together than Biden, 35% to 29%. Right now they're dividing the progressive vote. Biden leads, but is more of a moderate, center left ideological and has a history of working across the aisle to get things done. This, I don't think the Democrats will go for. Outside of Biden and Klobuchar, maybe Gabbard, all those running are basically far left progressive.
As the progressives drop out their support will go to Warren and or Sanders. Biden only hope is Warren and Sanders continue to divide the Northeastern progressive vote. Biden's strength is among the older folks and blacks. Not the white liberal/progressive crowd.