Yet Mr. Ackman is not like most of his peers. He has brushed off questions about whether his investors were worried and frustrated with his steep losses, countering that over time his firm had “a good batting average.” Together with his analysts, he told clients last week that the companies in which he has made big bold bets remain “unique,” “successful,” “fantastic” and “terrific.”

“We all know someone like him,” said Doug Kass of Seabreeze Partners Management, a small hedge fund firm. “Ackman is the smartest guy in the room who tells you he is the smartest guy in the room.”

It has helped that Mr. Ackman has structured Pershing Square so that investors have to wait as long as two years to take their money out. While some big investors have withdrawn their money recently, others believe that his firm will turn the corner.

The question is how much latitude investors will give to a man who fancies himself the next Warren E. Buffett. Over the last two years, investors have either withdrawn or announced plans to redeem more than $1 billion from his hedge fund, including New Jersey’s state pension fund, the Public Employees Retirement Association of New Mexico and the Fire and Police Pension Association of Colorado.

There is one mistake Mr. Ackman has admitted to making: Valeant Pharmaceuticals International. The drug company has come under political attack for its pricing policy and has faced regulatory scrutiny over its accounting practices. In April, Mr. Ackman was called to Washington to testify at a Senate hearing, where he was questioned over his aggressive support of the company. A flustered Mr. Ackman was forced to concede, “I regret that we didn’t do more due diligence on pricing.”