And let me chime in with the rest of the Centrists that third parties don't work. Theodore Roosevelt proved it, George Wallace proved it, Ross Perot proved it, Ralph Nader proved it..."this time" wont be different.
I think our best bet is to look at the dubious success of the Tea Party. Split the party from within and replace the moderates with the likes of Ocasio-Cortez. This is possible, doable, and currently underway.