Is it possible Markey fails to even be on the primary ballot?
Could very well happen.
And sorry, I misunderstood the article. It said
Markey has yet to collect 3'000, I finally found out that the threshold is 10'000 (thanks Politico). So JPK III is almost definetely on the ballot while Markey could still make it (there are still at least at least three weeks to go), and Markey would yet have to win the primary (he has been behind, albeit mostly narrowly, in all polls so far).
Likely Kennedy, closer to Safe than Lean.