It’s about African ethnicity more than albedo per se. GOP also-ran Vivek Ramaswamy is about the same hue as Obama but it’s less of an issue for him. Quite a bit of US racism lingers from the Jim Crow era and even the Civil War. Most African-Americans are literally descended from antebellum slavery and are still seen by some as something like escapees who need to be rounded up and put back on the farm. Obama himself didn’t have that in his ancestry (his father came to the US from Kenya, which didn’t “count”) and that helped him, I think, though of course he was still subject to racism. Basically there is a chunk of the US that misses the plantation system and wants it back.