Troubled OneUnited Bank in Boston didn't look much like a candidate for aid from the Treasury Department's bank bailout fund last fall.

The Treasury had said it would give money only to healthy banks, to jump-start lending. But OneUnited had seen most of its capital evaporate. Moreover, it was under attack from its regulators for allegations of poor lending practices and executive-pay abuses, including owning a Porsche for its executives' use.

Nonetheless,...