With its plush red couches, faux gold-leaf covered walls and $3.50 glasses of sparkling wine, the dimly lit Gold Dust Lounge is a holdout of old San Francisco in the midst of the upscale shopping district on Union Square.

News last week that the Gold Dust would be evicted in March, to be replaced by a mystery retailer, has raised a great hue and cry from the bar’s loyal local patrons and tourists alike.

“It’s like taking down one of the spans of the Golden Gate Bridge, it’s like shortening Coit Tower, it’s like dropping the Transamerica tower by 10 stories,” said Tim Chappelone, 64, a retired P.G.&E. employee. “The city will still be here, but it won’t be the same.”

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A lifelong San Francisco resident, Chappelone, who was drinking his favored $4 bourbon with water, said he had been coming to the Gold Dust for 40 years. He and his wife, Jennifer, heard about the impending closure from their daughter and read about it “on Google.”

In one short week, a robust campaign to save the historic watering hole has sprung up spontaneously on the Internet: the Save The Gold Dust Facebook page has nearly two thousand fans. There is also an online petition, a Twitter account and a blog dedicated to the cause.

A news conference is being organized with some of the bar’s more famous regulars, including former Mayor Willie Brown and Christopher Caen, son of the legendary Chronicle columnist Herb Caen, who preferred a double vodka on the rocks in a wine glass with a twist and soda on the side.

It was once part-owned by Bing Crosby — and it was also, perhaps, a speakeasy during Prohibition — but since 1965 the Gold Dust has been owned by two brothers: Jim and Tasios Bovis, now 79 and 82 respectively.

“It’s very sad — it’s been like a family,” said Jim Bovis as he sat at the bar with Gracia, his elegantly dressed wife, on Thursday.

Jon Handlery, president of Handlery Hotels, is the landlord who wants the Gold Dust out. Although he refused to identify the company, Handlery said he had a letter of intent to lease that space as well as the larger adjoining art gallery.

“Sometimes change can be challenging,” Handlery said, “but sometimes there’s opportunity for something better.”

Handlery said the prospective tenant would pay more in rent. He added that although “with today’s technology things spread around quickly,” the on-the-ground support for the bar was not as apparent.

“I often walk around the block,” he said. “It isn’t like there’s a line outside the Gold Dust to get in.”

But don’t count the Gold Dust out just yet. On the long list of San Franciscans’ causes, saving bars ranks very high, said Christopher VerPlanck, an architectural historian who engineered a recent effort to save the Tonga Room on nearby Nob Hill.

“There’s just such a long history of drinking in San Francisco,” said VerPlanck. “It’s that simple.”

This article also appears in the Bay Area edition of The New York Times.