As opposed to weeding out the base?
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Who said anything about weeding out the base? If the base cannot cope with folks who don’t think just like them, they will be forever an also-ran party.
How many people, not of the base, voted for Ronald Reagan? Quite a lot. Some were moderates and independents.
You lose the base you lose period. If you like to call the Clinton socialists “independent and moderate” so be it but you’re only driving the GOP left and the democrats further left.