Attributing Troubles to Newcomers
On the one hand, attributing Trump to an invasion of the Republican Party by Democrats sounds plausible to me.
On the other hand, blaming problems on newcomers appears to be one of the commonest failure modes in human thinking. This applies to opponents of immigration, opponents of gentrification, and opponents of colonialism. Maybe it also applies here.
Since I'm a human being (last time I checked), maybe I should not be confident in attributing Trump to Democrats.