Personally, I can’t wait until Newt Gingrich and Rick Santorum get offstage so we can start running a presidential campaign that isn’t based on trying to alienate the vast majority of Americans over irrelevant issues.

I’m referring of course to the Trayvon Martin case, where Newt and several other conservative loudmouths have managed to take a case that had absolutely nothing at all to do with Republicans and turn it into another brouhaha where the GOP are the bad guys.

Let’s go over the facts. A 17-year-old black kid who’s visiting in an Orlando suburb goes to the corner for a snack at halftime of an NBA All-Star Game. On his way back he is spotted by one George Zimmerman, a 28-year-old self-appointed neighborhood crime watcher who decides Martin looks suspicious, apparently because he’s never seen the kid before. Zimmerman calls 911, says he’s following someone he thinks may be a burglar, and is specifically told by the operator not to pursue the kid any further. He ignores this instruction, gets out of his truck and starts following Martin on foot. Zimmerman is inept enough so that the kid soon realizes he is being pursued. He calls his father’s home and tells them some strange guy is shadowing him. What happened next is under dispute. Zimmerman says he decided to go back to his truck and Martin jumped him. Maybe it happened, maybe it didn’t. In any case, the two end up fighting with Martin beating Zimmerman’s head into the sidewalk. At this point, Zimmerman pulls a gun and shoots Martin dead.

Not the kind of situation the shooter is likely to walk away from without some kind of investigation, right? But no, the Sanford police choose to take Zimmerman’s story at face value. Moreover, like 30 other states, Florida has a “Stand Your Ground” law, written mainly to protect homeowners but containing a clause saying a person can use deadly force if he fears for his life or from suffering “great bodily harm.” It’s an ambiguous situation where it would be nice to have a judge and jury decide. But the police decide to accept Zimmerman’s story and he walks. It doesn’t seem very logical. If Martin had wrested the gun away from Zimmerman and shot him, would he have gotten off so easily? He’d have a better case, since Zimmerman was obviously intending to use the gun on him. Well, I’ll let you decide that one.

So as anyone could have predicted, the case quickly becomes a cause célèbre. “No black teenager is safe,” “This is Emmett Till.” “It’s just like Mississippi in 1935.” Not quite true, but this is what happens when the police make dubious decisions like this one. So now we’re back to the situation where the federal government has to intervene against Southern racists and all this will probably stretch out into November.

The point is this. Republicans have no reason to intervene in this fight. Seventy-five percent of the public thinks Zimmerman should be charged with something. Second-degree manslaughter certainly sounds pretty good to me. This wouldn’t be “scapegoating,” as conservative talk show hosts are already nattering, it’s just common sense. Zimmerman wouldn’t be guilty of anything until tried by a jury, but it’s better than being tried in the newspapers. In any case, the idea you can gun somebody down in the middle of the street and just walk away doesn’t appeal to me and probably not to the vast majority, either.

I spent several years going out with a neighborhood crime watch in Brooklyn, a much tougher neighborhood than Sanford, Florida. One thing I can tell you is that every one of these patrols has at least one wannabe cop. This guy lives by the police radio, knows every officer by name, and is just itching to get out there and show he can collar a perp as well. Reining these people in is a principal tasks of the police advisors. “You never confront a criminal yourself. You never try to make an arrest. You never intervene in a situation. You are not a police officer. You are only there to observe. If you see something, call us and we’ll handle it.” That’s the mantra.

Zimmerman had pestered the station for months with reports of “suspicious 12-year-olds” walking through the neighborhood. He was an overenthusiastic pest at best. He was definitely headed out of bounds. That he would get out of his truck and shadow Martin after specific instructions of the 911officer is bad enough in itself. That he was doing this while carrying a gun in his pocket says to me he was definitely courting trouble.

And “Stand Your Ground” — what the hell is that supposed to mean? Once a fight begins, can’t Martin stand his ground as well? And if both can stand their ground, doesn’t it just become a contest of who is better armed? It sounds to me like the guy who brings the deadliest weapon wins.

In any case, why do Republicans have to get involved in this mess? Wouldn’t it be better to utter a few words of regret and move on to something more political? But no, good old Newt can’t miss the chance to alienate three-quarters of the American population. What sets him off is President Obama’s comment, “If I had a son, he would look just like Trayvon Martin.” What’s wrong with that? When President Obama went to Israel he said, “If somebody shot rockets at my house where my two daughters were sleeping at night, I’d do everything in my power to stop them.” Was that introducing sex and religion into international relations? No, he was just empathizing. That’s what Presidents are supposed to do.

But old Newt can’t let that pass. Like a big, lazy trout he jumps for the bait. Obama’s comment is “disgraceful” and “appalling,” “trying to turn this into a racial issue.” Good old Rick Santorum isn’t far behind, accusing Obama of “introducing divisive rhetoric.” So all of a sudden, it’s Obama versus the Republicans with three-quarters of the population on Obama’s side.

Look, just because President Obama says something doesn’t mean it’s wrong. Let’s not be naïve. George Zimmerman introduced race into the incident at the beginning when he decided to follow Martin because of the way he looked. If Martin had been a white preppie in a suit and tie, he never would have given him a second glance. Zimmerman is now trying to play this game himself, arguing that he couldn’t have done anything wrong because he’s half Hispanic. Let’s just forget all this pedigree stuff and concentrate on what happened.

But sure enough, once Newt has served up the ball, conservative commentators are rushing to Zimmerman’s side, trying to defend him from “scapegoating.” Rush Limbaugh says Obama is just using the case as a “political opportunity” and wonders why everyone is so excited about something that happened a month ago. Dennis Prager says Obama has “disgraced the Presidency” and compares Zimmerman to the falsely accused Duke rapists. Geraldo Rivera even suggests Martin brought it all on himself by wearing a hood. Glenn Beck discovers the kid was suspended from school for traces of marijuana. (Twenty percent of the youth population could be nailed on that one.) Then there are rumors that he was caught with some jewelry, that he entered an unauthorized school area and even wrote “W.T.F.” on a door. (The Sanford police have been good at leaking all this.) And all this is supposed to suggest he deserved to be shot?

And so the noble effort to unseat President Obama and save the country from economic ruin ends up stranded on the beach in a crusade to defend a Florida wannabe cop. There are two presidential candidates who have sensibly kept their noses out of this one. I won’t mention them by name but they are to be commended.

I spent five years writing a book about crime in the 1980s. Much of my research consisted of listening to liberals blather about how “Criminals are impulsive,” “They can’t be deterred,” “Punishment doesn’t work,” “They don’t think about what they do,” plus “Better a hundred guilty people go free than one innocent person be convicted.” And on and on. Liberals were wrong then, just as conservatives are wrong now for trying to keep Zimmerman from being charged with anything.

The justice system is a pageant. Each criminal trial is public theater from which people gather moral lessons. It matters whether people who commit offensive acts are arrested, tried, convicted or acquitted. Each case sets a standard for public behavior. When the public sees justice done, it reinforces everyone’s sense of morality. When people see others getting away with things, they become uneasy, demoralized and finally angry.

So what’s the example to be drawn so far from this particular episode? Well, ask yourself this. Suppose black people decided to absorb the lesson and start patrolling their own neighborhoods with guns, challenging every “suspicious” white person who comes along and relying on “Stand Your Ground” in case anything goes wrong? Would that bode well for the tranquility of the republic?

Cops want people to help them in preventing crime, make no mistake. They want tips, they want neighborhood watch groups and above all, they want people brave enough to stand up and testify in court — not an easy thing when you live in a neighborhood controlled by criminals. What they don’t want is eager-beaver vigilantes running around with guns trying to do their jobs for them.

That’s one lesson worth driving home in the Trayvon Martin case.

Mr. Tucker is author of Vigilante: The Backlash Against Crime in America.