Legg Mason, the money-running firm whose assets under management have fallen from $1 trillion to less than $700 million, billion, thanks to falling stock values and withdrawals from its funds, has entered a new phase. Underperforming public firms such as this are always under risk that an outside investor will decide he has better ideas about how to build shareholder value than the guys in charge.

Nelson Peltz, who has a long record of such agitation, has taken on that role at Legg. He has 4 percent of its stock now. Expect him to accumulate more. Financial types I talk to around town believe there is a decent chance that the firm Chip Mason built will not be independent in a couple years. If this turns out to be the case, Peltz's arrival will be the first step in this process.

But the sale of Legg is far from guaranteed. Legg is recovering on its own -- faster than the economy. Peltz may be satisfied with less-drastic outcomes. Here is part of today's column. Read the whole thing here.

The arrival of Peltz and his 4.3 percent ownership stake increases the uncertainty. Given what Legg has been through, it was hard to imagine that the pressure on Bill Miller and the firm's other money managers to perform could have been any greater. But it just intensified. "His appearance is not good news for management," says Charles M. Elson, a business professor and corporate governance expert at the University of Delaware. "But it may be good news for the shareholders."