John J. Mack stood before his board and shareholders at Morgan Stanley’s 2007 annual meeting and struck an aggressive tone. Coming off a year of record profits fueled by using the firm’s capital to take some highly lucrative risks  particularly by diving deeply into subprime mortgages, leveraged loans and complex derivatives  Mr. Mack had much to celebrate.

“Do we take a lot of risk? Yes,” he said forcefully, in response to a shareholder who questioned him about Morgan Stanley’s reliance on risky trades and increased debt to finance these positions. “I think this firm has the capacity to take a lot more risk than it has in the past.”

Next month, at Morgan Stanley’s annual meeting, Mr. Mack is unlikely to be so bold.

Having presided over close to $11 billion in write-offs and a wholesale revamping of Morgan Stanley’s risk management process, Mr. Mack faces an investor community that is raising questions about his ability to continue leading Morgan Stanley as he has.

The CtW Investment Group, a shareholder activist group representing union-sponsored pension funds with about $1.4 trillion, is weighing a campaign aimed at persuading Morgan Stanley investors to withhold their vote for Mr. Mack as chairman. The hope is to persuade Morgan Stanley’s board to appoint an independent chairman. An announcement of the effort could come as early as Wednesday.