Moral hazard became part of the national conversation in the financial crisis of 2008, when ordinary Americans wondered why they should rescue banks that helped drive the economy off a cliff. Now those same banks point to moral hazard to explain why they can’t do more to help people with mortgages. And it’s not just banks — the Tea Party movement was inspired by outrage over a government plan to, as Rick Santelli put it in a famous rant on CNBC, “subsidize the losers’ mortgages.”

The cherished American ideal of self-reliance has a flip side: discomfort with the idea of bailouts and safety nets. The notion that even a small portion of such aid might find its way to the undeserving can be enough to scuttle support, or restrict help so drastically that few can use it. The specter of moral hazard haunts a basic tension in American life: to what extent are people responsible for their own problems? The more trouble you’re in, moral hazard suggests, the less we should help.

Bankers say that generously easing loan terms or reducing mortgages outright would only encourage homeowners who can pay to pretend they can’t. It would also, the bankers say, send a dangerous message: a financial commitment isn’t really a commitment. Economists and policy makers say the bankers are right — but only to a point. Shaun Donovan, the secretary of the Department of Housing and Urban Development, said that there was a “nugget of truth” to the moral hazard argument. But he also said that the best evidence indicated that only about 10 or 15 percent of mortgage defaults were by homeowners still financially capable of paying their mortgages. Most troubled homeowners, like the Katrina victims, are genuinely hard up.

Kamala D. Harris, the attorney general of California, is adamant that homeowners are not looking to abuse the system. “I have met with these families,” she said, “and every single one of them wants to pay to stay in their homes.”

Still, the $26 billion deal that authorities struck with banks this month over foreclosure abuses — a main element of which will require the banks to reduce homeowner debt — angers some. Homeowners who keep paying their mortgages, even if their homes have lost value, reasonably wonder why neighbors who weren’t as responsible are getting help.