Buried in the data from the most recent Quinnipiac University polls is the popularity of Police Commissioner Ray Kelly among blacks. Some 68 percent of African- Americans polled approve of the job Kelly is doing, com pared to 51 percent for Mayor Bloomberg and 55 percent for City Council Speaker Christine Quinn. Kelly also polls well with Hispanic voters, earning a 62 percent ap proval rating, beating Bloomberg’s 50 percent, and Quinn’s 44 percent. It’s early to start handicapping, but Kelly’s as tonishing esteem among minorities could make him the frontrunner for mayor in 2013 — that is, if he wants the job and unless Bloomberg decides to run for a fourth term.