The national political press is fixated on the chaotic and contentious Republican presidential primary, and not without good reason. But in devoting so much focus to the race for the GOP nomination, the Democratic side of the aisle has been getting short shrift. Over the course of the summer, a left-wing revolt against and former Secretary of State Hillary Clinton has evolved into an insurgency, and her campaign is gradually imploding, albeit at a cosmically languid pace. But that tempo is set to accelerate. The tipping point may have been reached on Thursday when one of the presumptive Democratic nominee’s worst fears was realized.