Sen. Cory Booker has revived the debate over whether the existence of the filibuster actually prevented Obamacare from being repealed in 2017.

As liberals push Democrats to rally around a sweeping policy agenda, they are also confronting the reality that as long as there is a 60-vote threshold for passing legislation in the U.S. Senate, their transformational ideas such as socializing the health insurance system and imposing the Green New Deal will never become reality.