Trump is spouting racist rhetoric popular a century ago, like "racehorse theory" — see Trump Praises Good Genes for Haaretz's comparisons to the Nazi era.
(1) Another heavily used technique in modern politics is saying words that don't sound offensive in an offensive manner, until anti-racists hate the phrase and get rightfully angry each time they hear it.
(2) Then people who aren't paying much attention — unfortunately that's an awful lot of us, a lot of voters — are curious about or like the actual meaning of the words. They say the words or ask about them ...
(3) and anti-racists assume they are trolls and attack. This divides people who were apathetic about racism or are young and new to politics with the racists and away from the anti-racism team. They keep learning about the issues from the people who seem to be agreeing that of course all lives should matter.
— This tactic usually overlaps distracting conversations from the core point like turning a video of a police officer killing a black person into a weird and meaningless tangent about dictionary definitions.
— This tactic is related to dog whistles. Unlike past dog whistle politics, this is similar to handing out a dog whistle to someone who doesn't realize they're blowing in a dog whistle, causing them to get a reaction they didn't mean and don't understand.