The left has correctly identified the filibuster as a major obstacle to its agenda. Biden has been equivocal. Why?
For three interconnected reasons. First of all, the filibuster isn’t even an issue unless the Democrats win an effective (as opposed to a nominal–I will post on this tomorrow) majority in the Senate, which is a toss-up at this point. Second, Biden has great respect for the traditions of the Senate; there is no point in making clear statements that you’re in favor of blowing something up if it won’t do any good. Third, unity is Biden’s brand; it would be a mistake to jeopardize it unless it is absolutely necessary.
I suspect Biden, as president, will initially attempt to make deals with GOP senators, using the potential abolition of the filibuster as leverage if he plausibly has a Democratic majority in his favor. He would only campaign for its abolition if it is feasible and necessary to get his agenda through, and if GOP senators prove to be beyond redemption, which seems pretty likely.