DavidB at Gene Expression tackled the question yesterday of Winston Churchill's purported Jewish ancestry. A check of secondary sources revealed no such lineage.
The only serious gap in the official records of Churchill's ancestry is a long way back in the female line, which cannot be traced beyond his great-great-grandmother, Anna Baker. According to family legend, she was part-Iroquois Indian, which the family believed accounted for the prevalence of dark eyes or complexion in the family. This does have a certain whiff of cover-up, but if so the cover-up may be of something other than Jewish blood. According to one account, Churchill himself believed there was a drop of black somewhere in his ancestry (see Elisabeth Kehoe, Fortune's Daughters: The Extravagant Lives of the Jerome Sisters (2004), p.4). In any case, the usual claims of Jewish ancestry concern Churchill's mother's father, Leonard Jerome, and not the female line leading back to Anna Baker.He concludes that the claims stem from a parenthetical comment—probably tongue-in-cheek—in a 1993 article by Moshe Kohn.