Many people believe that down through American history, numerous “people who believe they are white” in American history were actually part black. A common example given both now and during his own lifetime is President Warren Harding.
Harding, who wished American blacks well and didn’t have any interest in making their lives harder, was a welcome change on the racial policy front from Woodrow Wilson, who devoted some fraction of his reforming zeal to making things worse for blacks. Harding publicly denied the Democrats’ charges about his ancestry; in private, he admitted that he didn’t know who every single one of his ancestors was and didn’t much care.
On the other hand, the more you think through the logic of the one drop rule that operated in most parts of what became the United States after the 1600s, the more you realize that passing from publicly being recognized as black to white was a difficult process, involving cutting yourself off from relatives, which few would undertake and fewer succeed at. DNA studies in recent years have found that only a few percent of non-Hispanic Americans who identify as white have even trace amounts of sub-Saharan African ancestry.
So, what about Harding? From the NYT:
The testing also found that President Harding had no ancestors from sub-Saharan Africa, answering another question that has intrigued historians. When Harding ran for president in 1920, segregationist opponents claimed he had “black blood.”So, chalk Harding up as additional evidence for the new scientific awareness that “people who believe they are white” are pretty darn white.