This has got to be one of the craziest races of the year, where an incumbent nearly goes "Bulworth" to win, while giving the Kennedy family their first loss in a Mass. state race with this Senate primary.
Kennedy was up by double digits in may, almost at 20 points. He is now losing by 10 as the votes come in. That may be a 30 point swing.
AOC and Sunrise. AOC basically flipped the race by cutting Kennedy off from younger voters with not only her endorsement of Markey, but Markey's embrace of her and the Green New Deal (Markey is the Senate co-sponsor of it). And The Sunrise Movement may very well be the most dangerous organization deployed against Democratic moderates, as they have helped sack 3 incumbents and win open seats for progressives. They basically provided the force behind Markey's campaign. As a result, progressives started making Markey, who was far more centrist in the past, cool and a bad-ass, and he added on to that image with his ads.
Meanwhile Kennedy stumbled, could not find a good answer to why he is running to unseat Kennedy, played of his family name too much, and exposed himself to brutal attacks by the Markey camp. Markey was able to define him as an opportunist using his family name. And Kennedy could not differentiate his positions from Markey, hurting him.
Overall, Mass. primary wasn't great for progressives, Alex Morse lost, progressives bungled a race for Kennedy's house seat that led to a former Republican winning, and Kennedy did win with the working class. But they won the big race and kept the Green New Deal Senate sponsor in office.