We started out overwhelmingly unified, and those are unifying factors. Reacting to fear with anger and blame is not exactly the same as becoming a Republican convert.
It also seems probable that some who consider themselves anti-Democratic progressives will fight the overthrow of progressive government by allying with Democrats. Common interests also a unifying force.
The strongest unifying forces of course arise from principles and conviction that most of us have, and would gladly share if we only could. (Hey, isn't that why we all come to political forums? 
)
But when we can't inspire them in others, at least, though demoralized people tend to vote in fewer numbers, frightened people vote to protect themselves and their own in larger.
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