These days our favorite television characters often display a moral ambivalence we refuse to tolerate in our elected officials, our friends or members of our family.

We call this moral ambivalence "character complexity" and consider it a good thing when it is grounded in popular narratives. It's what keeps us coming back. Relentlessly virtuous characters quickly wear out their welcome.

Remember when Andre Braugher's portrayal of Detective Frank Pembleton on NBC's "Homicide: Life on the Street" cornered the market on complexity in the early-to-mid 1990s? An admirable cop, but a very flawed and judgmental human being, Detective Pembleton was so morally inflexible that he was compelled to arrest his partner for murder in the series finale.

The legalistic complexity of Detective Pembleton soon gave way to the amoral complexity of suburban patriarch and mobster Tony Soprano in HBO's "The Sopranos" and the corrupt Detective Vick Mackey in FX's nihilistic cop drama, "The Shield."

There were charismatic villains in "Homicide," too, such as Erik Todd Dellums' untouchable drug lord Luther Mahoney. As much as we admired his slithery cool, we never cheered for him because he was so indisputably despicable.

It took ostensible good guys doing bad things to cause a shift in whom it was possible to root for and against. After 9/11, federal agent Jack Bauer's willingness to torture suspects on "24" seemed "reasonable" given the provocations of al-Qaida.

When Tony Soprano strangled a former associate relocated to New England by the federal witness protection program -- a task he handled while taking his daughter on a college visit -- we learned that a "likable" man could kill without remorse on a whim.

By the final season of HBO's revisionist western, "Deadwood," we were openly cheering Al Swearengen -- its brutal saloon owner, pimp and certified murderer played by Ian McShane -- because he was such a compellingly evil personality.

On the same cable network, "The Wire" perfected the art of making irredeemable folk such as Baltimore drug dealers, stickup men and burnt-out cops emotionally accessible to general audiences, something even "Homicide" never accomplished.

Michael C. Hall's portrayal of serial killer Dexter Morgan, who hunts other serial killers on Showtime's "Dexter," represents the extreme of our ability to give a fundamentally unsympathetic character a pass to do whatever's necessary for the public good. Dexter's bloodlust may be over the top, but it is so gruesomely specific that we're never threatened by it.

As great as these shows are, none has explored the arc of corruption that is the human condition with as much verve, moral seriousness and humor as AMC's critically acclaimed, but little seen, "Breaking Bad."

The show's premise explains why it is beloved by critics, but ignored by the masses: Walter White (Bryan Cranston) is a middle-aged husband, father and chemistry teacher in New Mexico. One day, Walt is startled out of his bland existence by a diagnosis of inoperable lung cancer.

Faced with the prospect of financial ruin from medical bills, Walt decides that the best way to provide for his family's future is to cook and distribute a particularly addictive form of methamphetamine. He enlists the help of small-time drug dealer and addict Jessie Pinkman (Aaron Paul), a dim-witted but somewhat street-savvy former student. For Walt, the end justifies the extremes he's willing to resort to for his wife, teenage son and infant daughter.

"Breaking Bad" is about what it takes to step over the line from a law-abiding middle-class existence to a life of self-conscious criminality. The series doesn't flinch from showing the carnage caused by meth addiction in America. It is never portrayed as romantic or bohemian, but always as a tragic waste of human life and potential.

Walter White is forced to respond in extreme ways to opportunistic and violent criminals who either want to kill him or compel him to work for them. As Walt moves up from meth cooker to drug lord in his own right, he discovers that his original rationale for turning to crime is no longer valid when his cancer goes into remission. Does he give up the money and return to a life of quiet desperation, or embrace his new identity with all the risk it entails?

Mr. Cranston has won three Emmys in a row for his portrayal of the morally conflicted Walter White. On Sunday, Mr. Paul beat the esteemed Mr. Braugher to take the best supporting actor trophy. The fact that they've won acclaim for roles that position them as the Batman and Robin of meth on a series very few have seen is a minor miracle. Season four debuts in July 2011.

The fall of Walt and Jessie is inevitable, of course. The only question is how many souls they'll take with them.

Tony Norman's weekly video, the Last Word, is featured exclusively in the Insight section on PG+, a members-only web site from the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.