Harding: The first African-American president?
Warren Gamaliel Harding, the 29th U.S. president, served from March 4, 1921 to August 2, 1923.
The American Decades reference source spoke of "attempts to arouse racist sentiment against (Harding) with accusations that his great-grandmother Elizabeth Madison was black and that his great-grandfather had African-American ancestors. While these claims were never definitively verified, they were widely accepted in the South."  One rumor went back a generation to say the Harding's great-great-grandfather was a "West Indian Negro." 
"Each generation of Hardings after (these great-grandparents)," wrote Theo Lippman Jr.  "as they grew up in Ohio in the 19th century, was teased and persecuted by schoolmates as 'part black'--and worse descriptives."
Although the family rejected these rumors, Warren Harding, who as a journalist had been dismissed by rival editors as a "kink-haired youth," "told at least one friend that he thought it might be true."
Segregationist William Estabrook Chancellor asserted that Harding's 1920 presidential campaign threatened to set up a "Haitian-style" United States government. Despite such efforts, Harding prevailed with 60 percent of the national vote.
In the South, however, where African-Americans seldom voted, Harding's numbers were much lower. only 32 percent of Alabamans, 23 percent of Texans, 14 percent of Mississippians and 3 percent of South Carolinians voted for his ticket.
When Harry Truman came onto the political scene, H.L. Mencken asked his brother's opinion of the politician. "He's a white Harding," the brother replied.
• SOURCES CITED:
"Warren Gamaliel Harding." American Decades. Gale Research, 1998. Reproduced in Biography Resource Center. Farmington Hills, Mich.: Gale, 2008. http://galenet.galegroup.com/servlet/BioRC. Accessed on Nov. 4, 2008.
 Lippman, Theo Jr. "Harding was the First 'Black President'." Baltimore Sun (Baltimore, MD),Oct. 7, 1998, p. 2A. Reproduced in SIRS http://sks.sirs.com. Accessed on Nov. 4, 2008.
 Here and remainder of this posting, ibid.