Wall Street’s debate over Bank of America’s purchase of Countrywide Financial is not whether it’s a good or bad deal—but whether it will be C.E.O. Ken Lewis’ last deal. “If this doesn’t work, at some point shareholders are going to demand Lewis’ head,” says Josh Rosner, managing director of Graham Fischer & Co., a New York research consultancy that specializes in mortgage finance.

But in keeping with the market axiom that any viewpoint unanimously held is wrong by definition, writing off Lewis so fast may be a mistake. In fact, there’s a decent—and obviously contrarian—case to be made that the Countrywide deal plays to Lewis’ strengths, if he can survive long enough to show them off.

First, Lewis is an old hand at big deals. Bank of America is the product of more than 3,000 mergers, and Lewis has worked on many of them, including the epic 1998 union of NationsBank (known as North Carolina National Bank when he started there in 1969) and Bank of America, California’s largest bank. It’s telling that most analysts were initially skeptical of the two Lewis megadeals that clinched Bank of America’s place as the country’s first (and still only) truly national consumer bank: the $48 billion acquisition of FleetBoston Financial in 2003 and the $34 billion purchase of credit-card specialist MBNA in 2005. In both cases, B of A was roundly criticized for overpaying. In the end, Lewis and his team squeezed so much value out of FleetBoston and MBNA in integrating them with B of A’s existing operations that investor opinion on the deals swung strongly to the positive.

Lewis also showed unusual resolve in sitting on his checkbook even as rivals were paying top dollar to buy mortgage lenders by the dozens in the 1990s. He was deeply ambivalent about the mortgage market, telling colleagues that he “loved the product and hated the business.” Although he acknowledged that the home loan was a “cornerstone of the customer relationship,” he considered mortgage lending unnecessarily risky. Not only did housing markets go from boom to bust all too often, but the structure of the industry was too risky because banks outsourced much of their lending to brokers or others.

As soon as Lewis moved up to C.E.O., he began restructuring Bank of America’s mortgage-lending operation with the dual aim of reducing risk and forging a closer, more lucrative relationship with his customers. Within a year, the bank had stopped making subprime loans and buying mortgages from other lenders. It also found ways to attract better-quality buyers: It trained about 10,000 personal bankers in its branches to sell home loans directly to consumers, along with checking accounts, credit cards, and certificates of deposit. This might not sound like much, but other banks relied on referrals from homebuilders and real estate brokers, which meant that they had less control over customer quality.

Lewis’ conservatism was tested during the housing boom that lasted from 2003 to 2006. Countrywide and other lenders fed the frenzy by amending conventional standards of creditworthiness to accept almost anybody willing to fill out a loan application (ability to repay optional). As lending volume exploded, the issue of whether B of A should jump back into the subprime game sparked fierce internal debate. Customers by the millions were going elsewhere for mortgages and taking their banking relationships with them. “You don’t want to be in a position where you have to say no to customers,” says a B of A executive who found himself on the other side of the issue from his C.E.O.