Mr. Biden added that the fate of the filibuster is “going to depend on how obstreperous they become,” meaning Republicans. In other words, if Republicans don’t agree to surrender to his agenda, Democrats will have no choice but to lay partisan siege to Senate rules.

On this as on so much else, Mr. Biden is going with the left-wing flow of his party. Democrats are increasingly confident that they’ll win enough seats to control the Senate in 2021. And if they do, they don’t want 47 or even 49 Republicans interfering with Democratic plans for the Green New Deal, making the District of Columbia a state, forgiving all student loans, and perhaps packing the Supreme Court, among so much more.

As Mr. Biden’s comments make clear, this prospect isn’t some GOP invention. Elizabeth Warren campaigned on it, and nearly all of the younger Senate Democrats agree. Chris Coons, the supposed centrist who holds Mr. Biden’s former Delaware seat, recently flipped his support for the legislative filibuster when Republicans control the Senate to favor killing it if Democrats take control. A few old traditionalists might object at first, but woe be the Democrat who opposes repeal if it comes up for a vote. The partisan pressure would be overwhelming.