On his pre-inaugural visit to Ben’s Chili Bowl, a landmark for Washington’s African-American community, President Barack Obama was asked by a cashier if he wanted his change back. “Nah, we straight,” Obama replied. The phrase was so subtle some listeners missed it. The reporter on pool duty quoted Obama as saying, “No, we’re straight.” But many other listeners did not miss it. A video of the exchange became an Internet hit, and there was a clear moment of recognition among many blacks, who got a kick out of their Harvard-educated president sounding, as one commenter wrote on a hip-hop site,...