CHICAGO (AdAge.com) -- McDonald's is rolling out McRib nationally. But before the product's rabid fans start rejoicing, let's make it clear -- the elusive product will be available widely only until Dec. 5.

That's by design, of course. The McRib -- a sandwich with a boneless pork patty molded into the shape of ribs and topped with barbeque sauce, pickles and onions -- has achieved cult status thanks in part to its scarcity. The brand typically pops up for a limited time on a regional or local level and has only been rolled out nationally twice before: in 1982, when it was introduced after a 1981 test-market run; and in 1994, for a McDonald's tie-in with the Flintstones movie.

The limited availability has created ardent McRib hunters, lovers of the sandwich who travel to find stores offering it. McRib superfan Alan Klein built the McRib Locator website and multiple Facebook pages have been created in celebration of the sandwich, and McDonald's is planning on whipping up that mad passion for the product in its national marketing campaign.

"Bloggers talk about the McRib, fans create websites to track it, and we want to capitalize on that. We want to keep the love for this product alive online, and we want fans to talk about the sandwich," said Brad Hunter, senior director-marketing for McDonald's USA.

In conjunction with its Nov. 2 national campaign rollout, McDonald's is launching a contest website (mcdonalds.com/mcrib), "The Legends of McRib," created by Omnicom's Tribal DDB. The site's name is based off the idea that the McRib isn't just a sandwich but a legend in its own right, and McDonald's is encouraging fans to submit their own stories of the McRib's legend, which don't necessarily need to be true, or even possible. The author of the winning submission will win a trip to Germany -- the only country where the McRib is offered 365 days a year -- and will also get his or her story animated into a motion comic that may appear on McDonald's digital properties. The website will be supported through online and social-media efforts, events and blogger outreach, among other marketing pushes.

Despite the national rollout, McDonald's has no plans to permanently add McRib to the menu. After all, absence makes the heart grow fonder. "To keep it relevant and appealing to our customers, it will continue to be offered as a limited-time promotion,"said Ashlee Yingling, spokesperson for McDonald's USA.

With fast feeders feeling the economic downturn, many are looking toward promotions to boost sales. "Chains like to have new-product news, and often that news is that they'll offer discounted items and value meals," said Mary Chapman, director-product innovation at Technomic. Other limited-time McDonald's promotions include its Monopoly game and Shamrock Milkshake.

McDonald's comparable sales in the U.S. were up 5.3% -- and 6% worldwide -- in the third quarter. The company cited its success with the McCafe Frappes and Smoothies as key contributors to comparable sales growth. In the first half of 2010, McDonald's spent about $529,000 on U.S. measured media for the McRib -- a sliver of the $441.3 million it spent in total for the same period. In 2009 the company spent about $3.3 million on U.S. measured media for the McRib, and about $3.4 million in 2008.

Aside from the Legends of the McRib website, McDonald's is reprising its general-market TV spot that aired in September 2008, called "Love" by Havas' Arnold Worldwide, showing people lovingly eating McRib. The company will also run a Hispanic-targeted TV spot from Omnicom's Alma DDB; an Asian-American spot from Interpublic Group of Cos.' IW Group; and an African-American spot from Publicis Groupe's Burrell. TV spots are expected to run through Nov. 22 and all carry a love theme.