PHOENIX -- Smitty's Super Valu here has introduced a Super "S" promotion in which it guarantees that its weekly advertised prices will be lower than the prices of virtually all its competitors. The offer, introduced in mid-October, encompasses 20 to 25 items included in the chain's weekly circular. All ad items are tagged in the store with Super "S" signs, and if any competitor's price beats Smitty's price on those items, the chain will lower its price, Mark Weidinger, vice president of marketing for the 27-unit chain, told SN. The offer includes advertised prices at Abco, Albertson's, Bashas', Fry's, Safeway and Smith's Food & Drug Centers, Weidinger said. (Smith's does not run weekly ads but guarantees to match all other chains' ad prices at store level.) During the first three weeks of the promotion, Smitty's has had to lower only one or two prices, Weidinger said. The only local competitors excluded from Smitty's offer are Megafoods and Southwest Markets.