The second theory of change is defection, where voters believe they can force a loss on either the Democrats or the Republicans, and thus make that party adopt their preferred policies, rather than face another such loss in the future.
There’s No Such Thing As A Protest Vote
Clay Shirky

if the democrats lose to a terrible candidate like trump, theyll never win again until they change their tune. thats ok with me. let them never win again and let a real left wing party emerge in its ashes.