The negative ads on Bernie Sanders practically write themselves, but Hillary Clinton didn’t run any in 2016, probably because she was sure she would win in the end. 2020 will be a different animal, as Bernie will start the race as a favorite. Both Biden and Warren will have plenty of incentive to go negative; Bernie is a direct threat to both of them. Will they do it?
Not immediately. Warren’s campaign will wither and die, leaving Bernie as the king of the class/fundi quadrant. If Bernie and Biden emerge as the last two standing, Biden will probably decide to take the risk of alienating the left and will start running ads starring the Castros and Daniel Ortega.