NEW YORK (CNNMoney.com) -- General Motors is preparing to announce that the Pontiac car brand, once marketed as GM's "Excitement division," will be killed off, according to a source familiar with the decision. An official announcement is expected Monday. GM spokesman Jim Hopson declined to comment on Pontiac's fate, saying the automaker has no announcements to make at this time. In its most recent "viability plan" - which will be updated to reflect this new brand cut - Pontiac was not named as one of GM's four "core brands." Those are Chevrolet, Buick, GMC and Cadillac. But Pontiac was also not to be killed or sold off, as were Saturn, Saab and Hummer. Instead Pontiac was to continue on as a "niche brand" focusing on just a few models. That was already a step down for Pontiac which in 2008 was the third-best selling brand behind Chevrolet and GMC. That year the brand sold more than Cadillac and twice as many vehicles as Buick. Cadillac is a high-profile - and high profit - luxury brand while Buick is a hugely popular brand in China and is seen as resurgent in the United States. In 2005, GM (GM, Fortune 500) vice-chairman Bob Lutz referred to Buick and Pontiac as "damaged brands" during a conference at the New York Auto Show. That set off speculation that one or both of these brands was doomed. With a focus on affordable luxury, Buick's hopes have been revived by models like the popular Enclave crossover SUV. Improvements in Buick Quality, which earned a top ranking in a recent J.D. Power dependability survey and a public acknowledgement by President Obama, have also helped Buick keep its place in the shrinking pantheon of GM names. Pontiac performance Pontiac's association with performance dates back to the late 1950s and early 1960s. Pontiac cars were designed with wider bodies for cosmetic reasons and the wheels were pushed out to match. This "wide-track" design became a selling point and was advertised as giving Pontiac cars a distinct cornering advantage over other cars. But the idea of Pontiac as a performance brand was solidified in 1964 with the creation of the Pontiac Tempest LeMans GTO. That car quickly evolved into, simply, the GTO and is often credited with creating a new class of American car, the muscle car. Under Lutz, plans were formed to bring back some actual excitement to the Pontiac brand, which hadn't seen much since the Firebird - a flashier Pontiac version of the Chevrolet Camaro - ended production in 2002. One strategy floated for Pontiac was to sell only, or mostly, rear-wheel-drive cars. That would set it apart from other GM divisions, and most cars sold in America. Rear-wheel-drive is associated with performance brands like BMW. Unfortunately, the re-introduction of the Pontiac GTO name on a performance coupe imported from Australia didn't result in big sales. So far, the Pontiac G8, a rear-wheel-drive four-door sedan also imported from GM's Australian Holden division, hasn't been a sales success either, despite good reviews. Pontiac's most popular products remain the G6, a decent but unexciting midsize car available as a sedan, coupe or convertible, and the Vibe, a small wagon shared with Toyota, which sells it as the Matrix. Any plans to return Pontiac to the heavy-horsepower days of the '70s ended as gas prices rose and Congress prepared stricter fuel economy rules for the industry. Those pressures resulted in GM quietly introducing the Pontiac G3, which had been sold in Canada only. Once again, Pontiac was selling a rebadged Chevrolet product, this time the Korean-built Aveo subcompact car. Pontiac's current role in GM seems mostly to be to support GMC and Buick by providing a brand under which Pontiac-Buick-GMC dealers could sell non-luxury cars, filling out what then becomes a full-line showroom. The brand-channel strategy now makes it easier for GM to phase out the brand because it would cause less harm to dealers, independent business protected by strong state franchise laws. When GM phased out Oldsmobile in the early 2000's, it cost GM more than $1 billion to buy out the contracts of Oldsmobile dealers who were left with nothing to sell. This time, most Pontiac dealers will have other products to sell.