In a comfortable ranch home not far from Route 20, the Williams family gathered around the television. Doug, his wife, Raunda, and son D.J. watched the pomp and circumstance unfold in Washington, D.C. It was Martin Luther King Day and Barack Obama was solemnly swearing on two bibles — one, formerly owned by King himself, the other by Abraham Lincoln — that he would faithfully execute the office of the President of the United States for another four years. Two of the Williams girls, Laura, 7, and Lee, 4, covertly jousted with sharp elbows, their brown eyes gleaming with glee, if not understanding. Some day, they will grasp the significance of the moment. They will also learn that their father has a special place on this continuum. “Absolutely,” said Dr. Harry Edwards, a University of California-Berkley sociologist. “I think we have to understand the history of sports’ contribution to the broader culture.” There is a direct line of ascent, Edwards said, from Jackie Robinson to Bill Russell, to Jim Brown to Curt Flood to Doug Williams to Barack Obama. Twenty-five years ago, he was breaking barriers. Now, Doug Williams coaches a new generation at Grambling, his alma mater. It has been 25 years since Williams led the Washington Redskins to victory in Super Bowl XXII, becoming the first African-American quarterback to win the ultimate football game.