The private equity firm, co-founded and run by Mitt Romney, held a majority stake in more than 40 United States-based companies from its inception in 1984 to early 1999, when Mr. Romney left Bain to lead the Salt Lake City Olympics. Of those companies, at least seven eventually filed for bankruptcy while Bain remained involved, or shortly afterward, according to a review by The New York Times. In some instances, hundreds of employees lost their jobs. In most of those cases, however, records and interviews suggest that Bain and its executives still found a way to make money.

Mr. Romney’s experience at Bain is at the heart of his case for the presidency. He has repeatedly promoted his years working in the “real economy,” arguing that his success turning around troubled companies and helping to start new ones, producing jobs in the process, has prepared him to revive the country’s economy. He has fended off attacks about job losses at companies Bain owned, saying, “Sometimes investments don’t work and you’re not successful.” But an examination of what happened when companies Bain controlled wound up in bankruptcy highlights just how different Bain and other private equity firms are from typical denizens of the real economy, from mom-and-pop stores to bootstrapping entrepreneurial ventures.

Bain structured deals so that it was difficult for the firm and its executives to ever really lose, even if practically everyone else involved with the company that Bain owned did, including its employees, creditors and even, at times, investors in Bain’s funds.

Bain officials vigorously disputed any notion that the firm had profited when its investors lost, arguing that a full accounting of their costs across their business would show otherwise. They also pointed out that Bain employees put their own money at risk in all of the firm’s deals.