In his memoir, Barack Obama omits the full name of his mentor, simply calling him "Frank." Now, the truth is out: Never has a figure as deeply troubling and controversial as Frank Marshall Davis had such an impact on the development of an American president.

Although other radical influences on Obama - from Jeremiah Wright to Bill Ayers-have been scrutinized, the public knows little about Davis, a card-carrying member of the Communist Party USA, cited by the Associated Press as an "important influence" on Obama, one whom he "looked to" not merely for "advice on living" but as a "father" figure.

While the Left has willingly dismissed Davis (with good reason), here are the indisputable, eye-opening facts: Frank Marshall Davis was a pro-Soviet, pro - Red China communist. His Communist Party USA card number, revealed in FBI files, was CP number 47544. He was a prototype of the loyal Soviet patriot, so radical that the FBI placed him on the federal government's Security Index. In the early 1950s, Davis opposed U.S. attempts to slow Stalin and Mao. He favored Red Army takeovers of Central and Eastern Europe, and communist control in Korea and Vietnam. Dutifully serving the cause, he edited and wrote for communist newspapers in both Chicago and Honolulu, courting contributors who were Soviet agents. In the 1970s, amid this dangerous political theater, Frank Marshall Davis came into Barack Obama's life.Aided by access to explosive declassified FBI files, Soviet archives, and Davis's original newspaper columns, Paul Kengor explores how Obama sought out Davis and how Davis found in Obama an impressionable young man, one susceptible to Davis's worldview that opposed American policy and traditional values while praising communist regimes. Kengor sees remnants of this worldview in Obama's early life and even, ultimately, his presidency.