Bernie Sanders was operating on all cylinders in this last primary. There is a documentary on all the efforts by his own party to stop his progress. In the end, the turnout was superb but it still was not enough because the older generation did not want take a chance on the radical policies that Sanders proposed.

So no the idea of a primary challenge is a lost cause and the younger generation internalized it this past election.

[1]: https://www.youtube.com/watch?v=fAfMn2l3yAA