As soon as Washington Mutual (NYSE: WM) evaporated, the natural question was: "Who's next?" And after its stock plunged 38% during the day, it now looks like the next one to go will be Wachovia (NYSE: WB). This time the buyer could be Citigroup (NYSE: C),

With $120 billion in adjustable rate mortgages (ARMs) it got through its Golden West Financial acquisition, Wachovia is particularly vulnerable to the capital-eroding impact of a drop in their value. But if Citi bought Wachovia, it would get a stronger presence on the East Coast and its well-regarded retail banking management.

Citi is not the only firm to talk merger with Wachovia -- prior to its decision to turn itself into a bank holding company (BHC) on Sunday, Morgan Stanley (NYSE: MS) was in merger discussions with Wachovia. I just wonder how any deal could be struck with Wachovia that would not involve those nasty ARMs. And if those ARMs are involved in a deal, how can the acquirer avoid those nasty digestion problems that have sent Wachovia shares into a dive.

Peter Cohan is President of Peter S. Cohan & Associates. He also teaches management at Babson College and edits The Cohan Letter. He owns Citigroup stock and has no financial interest in the other securities mentioned.