In the years before the recession, private-equity firms put so much faith in the future of U.S. brick-and-mortar retailers that they spent $36 billion on them.

That hasn’t worked out so well, especially for the era’s biggest spender, Bain Capital LLC. The firm started by Mitt Romney inked four deals valued at $17 billion from 2004 to 2007 and still owns all of the purchases. The largest of the bunch was Toys “R” Us Inc., which posted a drop in sales during the holidays, followed by Chief Executive Officer Gerald Storch stepping down.

The private-equity model -- load up an acquisition with debt, cut costs and take it public -- hasn’t gone according to the usual script with most of Bain’s retail acquisitions. That’s largely because the firm, which has $67 billion in assets under management, doubled down on specialty retailers just as they were about to be pummeled by the likes of Inc.

“There isn’t anything special about specialty anymore,” said Leon Nicholas, an analyst for Kantar Retail in Boston. Their advantages on product assortment, expertise and price have disappeared, he said.

Bain tried to take Toys “R” Us public in 2010 and then postponed the offering.

Of the eight largest retail private-equity buyouts during that period, only Dollar General Corp., a chain of discount stores acquired by KKR & Co., has gone public. Among the specialty retailers that remain private: Apollo Global Management LLC’s Claire’s Stores Inc.; the Sports Authority Inc., controlled by Leonard Green & Partners; and Petco Animal Supplies Inc., owned by Leonard Green and TPG Capital.

Raised Doubts

The fortunes of several large publicly traded specialty chains have only raised more doubts about these companies reaching an IPO. Borders Group Inc. and Circuit City Stores Inc. didn’t make it out of the recession. Many of the survivors have dubious futures and depressed stock valuations. Barnes & Noble Inc. and Best Buy Co. are losing money and aren’t increasing sales. While Staples Inc. made money and boosted sales last quarter, it has lost about a third of its market capitalization in two years.

“You look down the list of companies and the evidence is there” that the business model is in trouble, said Chris Bertelsen, who oversees $1.7 billion as chief investment officer of Global Financial Private Capital in Sarasota, Florida.

Alex Stanton, a Bain spokesman, declined to comment, as did Kathleen Waugh, a Toys “R” Us spokeswoman.