Four years ago, black Americans mobilized to elect one of their own president of the United States. When asked, the overwhelming majority of black Americans still say they support Barack Obama. But the old enthusiasm has dwindled.

The economic crisis of 2008 hit black America hard, and the recovery since 2009 has largely passed black America by. Black unemployment rates look like something out of the Great Depression: Almost half of young black men cannot find work.

The cool, cerebral Obama does not much comfort or inspire those out of work, black or white. He is not an "I feel your pain" kind of politician.

While nobody doubts that Obama will carry 90% or more of the black vote in November, a lot of people have wondered how high the black turnout will be. If dispirited black Americans stay home in large numbers, Obama's re-election challenge becomes that much greater. But what could possibly inspire them to the polls?

The answer may have just arrived -- in the tragic form of the killing of a teenaged boy, Trayvon Martin.

Three weeks ago, young Martin was shot and killed by a neighbourhood watch volunteer in a gated community in the town of Sanford, Florida. Martin was black, the volunteer was of white-Hispanic background. Martin was unarmed. He was 100 pounds lighter than his killer. At the time of the shooting, he was walking back to the house in which he was staying, talking on his cellphone, and carrying a bag of candy he had just bought at a nearby store.

The more details emerge, the more it looks as if Martin was hunted and killed by a trigger-happy bully.

Yet local police have not arrested the killer. No charges have been laid. The killer claimed to have acted in self-defence, and despite many problems in his story -- including the killer's own violent history -- the police opted to believe him.

Like nothing else since 2009, the Trayvon Martin case has jolted black America. Tens of thousands of people have signed digital petitions demanding a federal investigation. Demonstrations have begun to take place in Florida and elsewhere. A community that has had much reason since 2009 to ask, "Why bother with politics?" suddenly has found an answer.

Martin's killer, George Zimmerman, could plead self-defence because of Florida's peculiar gun laws. Under the old law inherited by the English-speaking world, an armed man has a "duty to retreat." Not in Florida. In 2005, Florida adopted what's called a "stand your ground" law. These laws -- increasingly common in southern states -- permit an armed man to shoot in self-defence even if he could have avoided the fight without shooting.

"Stand your ground" laws become especially lethal when combined with other new laws that grant people in the majority of U.S. states the right to carry weapons in public, and even concealed weapons.

U.S. gun laws have become more permissive even as U.S. crime rates have sharply declined. Why?

You can read the answer on the past four years' worth of front pages on the hugely popular website, the Drudge Report. Month in, month out, Drudge spotlights gruesome black-on-white crimes. In a country of 300 million people, there are always examples. These same stories circulate in e-mail chains -- and often become the focus of local right-wing talk-radio shows.

The U.S. journalist Mickey Kaus calls it "under-news:" news that never quite emerges into the national media, but that shapes the consciousness of millions of people. And what is being shaped is a conviction among many white people -- especially fearful elderly whites in the South -- that the Obama presidency has licensed a rampage of black-on-white violence. That's not what the statistics say. But as Stephen Colbert would say: Statistics are elitist.

As is so often the case, Rush Limbaugh gave these new racial fears their most explicit voice. In September 2009, after Drudge publicized an assault on an Illinois school bus, Limbaugh had this to say: "It's Obama's America, is it not? Obama's America -- white kids getting beat up on school buses now."

This mood of "backlash" has dominated U.S. politics since 2009 -- until now. Now the "backlash" has created an apparent martyr in Trayvon Martin. And it is in Martin's name that the backlash against the backlash will be launched and be heard.

You think the 2012 election will be about economics? Think again.

*This article previously appeared in the National Post

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