It's because of he's being Lucy with the filibuster reform football. McConnell dragged him over to the Dark Side. XD
Perhaps Dingy Harry is thinking about his future role as Minority Leader.
Better: retired.
That's a value judgment with which I concur; however, you are missing my point. Dingy and a bunch of other Democrats are loath to abolish the filibuster since they want to have it available the next time they need it.