Given all that yakkety-yak about the emergence of a new era of postracial politics, you might have hoped that by now, even the looniest of ultraconservatives might have figured out a way to criticize Barack Obama without sounding like howling race-baiters. Keep hoping.

Conservative dependency on racial resentments is so deeply ingrained that even phony members of the lunatic fringe, such as Donald Trump, can't resist the temptation. Like junkies, they're hooked.

Trump -- who has thrown far more campaign contributions to Democrats than to Republicans over the years -- is only pretending to be a right-wing Republican aspirant for the presidency. The fact that he has risen to the top of the polls among GOP voters by playing the race card reminds us that we're still stuck in the muck.

The racial subtext of Trump's much ballyhooed investigation of Obama's birth certificate (on which I'd wager he never actually spent a dime) was obvious from the start. His subsequent smear of Obama's supposedly substandard academic performance in college and at Harvard Law School is equally low.

Trump, who boasts about his good relations with "the blacks" as he boasts about everything else, is trying to insinuate that Obama is a product of affirmative action -- or, to put it more bluntly, that Obama is a stupid Negro who took the place of a better-qualified white person like himself.

In reaction, even straitlaced white newsmen like CBS's Bob Schieffer have thrown aside their objectivity to publicly denounce the "ugly strain of racism" in Trump's campaign.

Republicans, of course, don't have a complete monopoly on this noxious habit. But since 1964 -- when Barry Goldwater urged Republicans to "go hunting where the ducks are" by opposing civil rights legislation -- the GOP has been cornering the market on race-baiting. Every successful Republican nominee since then, with the sole exception of George W. Bush, has sailed into the White House on a tide of racial resentment. It has become such a habit that Republicans just can't kick it, even when their wiliest strategists, like Karl Rove, try to persuade them to go cold turkey.

Rove's motives have more to do with pragmatism than with morality. He knows that in an increasingly black, brown and beige America, the politics of white resentment will soon start to pay diminishing returns.