"Americans, claim Hopkins and Washington, have actually become less inclined to express racist opinions since Donald Trump was elected. Anti-black prejudice, they found, declined by a statistically-insignificant degree between 2012 and 2016, when Trump was elected. But then after 2016 it took a sharp dive that was statistically significant. Moreover, contrary to their expectations, the fall was as evident among Republican voters as it was among Democrats. There was also a general fall in anti-Hispanic prejudice, too, although this was more evident among Democrat voters."
The sharp, statistically significant decline is causally linked to Trump's election.