Twice Scott Brown and Elizabeth Warren have faced off in televised debates, and twice the Massachusetts Senate candidates traded blows over Warren’s claim to American Indian ancestry within seconds of the opening bell. The Republican incumbent and his Democratic challenger have launched dueling campaign ads calling even more attention to the issue, and there has even been a mini-kerfuffle over the low-rent antics of a few Brown staff members, who were filmed war-whooping and tomahawk-chopping at a campaign event in Dorchester.

Plainly the question of Warren’s Cherokee heritage isn’t going away any time soon. I’ll be surprised if she and Brown don’t sink their teeth into it again when they meet for Debate No. 3 in Springfield on Wednesday.

Maybe this time, for a change, they can focus on why it matters: not because race and color count, but because they never should.

One reason the issue doesn’t matter is Warren’s looks. “Professor Warren claimed that she was a Native American, a person of color,” Brown said less than 30 seconds into his first answer at their Sept. 20 debate in Boston. “And as you can see,” he added, pointing to his blond-haired, blue-eyed rival, “she’s not.” It was a cringe-inducing moment. Does the junior senator from Massachusetts really think he can “see” racial identity? Does he believe that American Indians – or Asians, or African Americans – can be infallibly distinguished by their physical characteristics?

Then again, Brown isn’t the only candidate in the Massachusetts Senate race who seems to think physical appearance equals racial corroboration. Warren does too. When controversy erupted in the spring over the fact that she listed herself for nearly a decade in the Association of American Law Schools directory of “minority law teachers,” she told reporters that her grandfather “had high cheekbones like all of the Indians do.”

To be fair, Warren hasn’t repeated that comment. And Brown now denies implying that his opponent can’t be a Native American because she doesn’t look like one – “I never made that suggestion at all,” he told reporters.

But neither campaign has let the issue die.

For months Republicans have had a field day with Warren’s claim to be Cherokee on the strength of unverified “family lore” about her great-great-great grandmother. Brown’s TV spot

milks the “Fauxcahontas” angle with clips of news stories reporting on the story. “Warren admitted to identifying herself as Native American to employers,” one broadcast journalist says. “Something genealogists said they have zero evidence of,” intones another. Firing back in her own 30-second commercial, Warren accuses Brown of vilifying her parents. “Scott Brown can continue attacking my family,” she says, speaking directly to the camera, “but I’m going to keep fighting for yours.”

None of this would matter if it weren’t for the fact that nearly half a century after the 1964 Civil Rights Act outlawed discrimination on the basis of race, racial discrimination – in the form of affirmative action – is entrenched in American society. Warren insists that she “never got any benefit because of my heritage,” and that the only reason she listed herself as an American Indian in professional law-school directories was to be invited to lunches “with people who are like I am.” Her explanations provoked so much ridicule because they were ridiculous. Everyone knows that minority status can confer serious advantages when employers place a premium on “diversity,” and use racial preferences and set-asides to achieve it.

Martin Luther King memorably dreamed of a nation in which people would be judged by the content of their character, not the color of their skin, and in much of American life his dream has become a reality.

But not within the contemporary diversity industry, where individual men and women are first and foremost members of categories, to be grouped by race, by ethnicity, by color. That’s the logic behind a directory of “minority law teachers.” It was also the mindset behind Jim Crow and “separate but equal.”

The real significance of Warren’s supposed Native American heritage isn’t that she lacks proof that one of her 32 great-great-great grandparents was a Cherokee. It isn’t that she believes the stories she was told as a girl. It isn’t that by identifying herself as a racial minority she may, in Brown’s words, have seized “an advantage that others were entitled to.”

It is that in 21st-century America, no such advantage should exist. Racial preferences should by now be artifacts of history, not tools for hiring law professors. Two generations ago Thurgood Marshall and the NAACP declared that “classifications and distinctions based on race or color have no moral or legal validity in our society.” Do the Massachusetts Senate candidates agree or disagree? Now there’s a question worthy of debate.

(Jeff Jacoby is a columnist for The Boston Globe. His website is www.JeffJacoby.com).