This is how the Tea Party and MAGA co-opted the Republicans, and it's the model progressives should use to move the needle in the Democratic party (and they have, with some success).
If progressives want to see change, progressives need to vote. In every election. General or primary.
You can also vote the Democratic primaries, too.
That worked out, suprisingly well, for Sanders. Think about how much change you could affect voting for Sanderses at every level.