You’re thinking of Vice Chair David Hogg.

Hogg pledged to primary ineffective democrats and the party crucified him for it. Current chair Ken Martin opposed this, proposing a change to bylaws that would require impartiality in primaries.

I am firmly with Hogg on this. Progressives need to be supported and conservative Democrats purged. Republicans with a D next to their name are no less an existential threat than those with an R. I don’t see Ken Martin as promising in any way whatsoever.