The Great Atlantic & Pacific Tea Company is rolling out a new advertising campaign starring president and CEO Sam Martin, who walks through the stores explaining the improvements the chain is making as a result of its turnaround efforts. Themed “shopping just got a whole lot better,” it marks the first time A&P will use one marketing effort for all its brands, including A&P, The Food Emporium, Pathmark, Superfresh and Waldbaum’s. Digital components started last month; TV is launching now, with 30-second spots running in New York and Philadelphia, as well as on such stations as HGTV, E!, The Food Network, Lifetime and TNT.