Arguably, no previous U.S. president has had as many disconcerting friends and associates as Barack Obama. Many Americans know of Reverend Jeremiah Wright, Bill Ayers, and Rashid Khalidi, but few have heard of perhaps the most important figure in Obama’s life: Frank Marshall Davis. Who was Frank Marshall Davis? In The Communist: Frank Marshall Davis: The Untold Story of Barack Obama’s Mentor, historian Dr. Paul Kengor writes, “[He] was a pro-Soviet, pro-Red China, card-carrying member of Communist Party. … He did endless Soviet propaganda work in his newspaper columns, at every juncture agitating and opposing U.S. attempts to slow Stalin...