Question: Using a positive as a suspicious negative.

I'm not sure, but if I am understanding this right, it may be a guilt by association fallacy. Since Democrats want something, and Trump (the bad guy) wants that same thing, Democrats are bad and conspiring with Trump for some bad eventual goal.
https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/10/Ad-Hominem-Guilt-by-Association