Historically, BofA has promoted from within. And internally the leading candidates appear to be Brian Moynihan, the chief of consumer and small-business banking, global markets head Tom Montag, and Barbara Desoer, president of the banks’ mortgage line.

Moynihan has been viewed as an heir apparent to Lewis for months. But Plath says Lewis’ swift exit may leave Moynihan, a former FleetBoston lawyer who only this summer took the reins of consumer banking, unprepared for such a large task. Other internal candidates also have blemishes.

Speculation is mounting that the bank may for the first time in 50 years turn outside for the next CEO. And the leading name among external candidates is former BofA CFO and current GMAC Financial Services CEO Al de Molina. “He’s got a good reputation with regulators, and he knows BofA,” Plath says. “He’d be my top candidate among outsiders, because he’s not a true outsider.”

De Molina, a Charlotte resident, could not be reached for comment.

Nancy Bush, analyst and founder of NAB Research, says the most likely scenario may be the hiring of a seasoned veteran from outside the bank who will soothe all parties. Meanwhile, an internal, long-term replacement will be groomed. In that case, Bob Steel, the former Wachovia CEO and U.S. Treasury official, and retiring Wells Fargo chairman Dick Kovacevich have been mentioned as possibilities.

“Kovacevich has enormous credibility,” says one analyst who asked to remain anonymous. “I just have a hunch that guy isn’t out of the game just yet.”

But observers also note that just because a candidate is acceptable to regulators and the bank’s board won’t guarantee the hiring.

“They have to want the job,” says Thomas. “Who’s going to want the job if it’s the government telling them what to do?”