Despite centuries of progress, women and blacks are still at a disadvantage in today’s America. The current presidential race, as it shapes up, can lead to some rethinking and maybe decisive improvement.

Women as a class are paid less than men for equal work and have less chance of promotion. Blacks, too, are paid less and promoted less than whites.

Both of these population sectors have benefited from legal changes giving them the right to vote and laws and regulations intended to guarantee fair employment practices and forbid discrimination. Both also benefit from a widening public acceptance of political and social equality.

In presidential politics, both women and blacks already have made their marks. Geraldine Ferraro, a Democrat, ran as Walter Mondale’s vice presidential running mate in 1984 and Maine’s Margaret Chase Smith was a Republican candidate for president in 1964. Jesse Jackson won five primaries and caucuses in 1984 and 11 in 1988 in races for the Democratic presidential nomination. The two glass ceilings have been cracked but not broken.

As Hillary Clinton and Barack Obama emerge as the Democratic front-runners, racial and gender issues inevitably emerge as well. Among the latest is a trumped-up controversy over which was the more important of the heroes of the fight to pass the Voting Rights Act of 1964, the Rev. Martin Luther King Jr. or President Lyndon Johnson, an episode that ended thankfully this week with both campaigns apologizing for their mistakes. The media, intent on seeing racial and gender overtones in nearly every utterance, has yet to apologize for making too much of Sen. Clinton’s comments that started the made-up furor. And far too much has been made of Sen. Clinton’s “likability” and episodes of tearfulness.

Either Sen. Clinton or Sen. Obama looks at this point most likely to win the Democratic nomination and, barring some unexpected development, the presidency.

Either outcome will be a major step forward for the growth of American democracy and a new U.S. signal to the rest of the world. To have reached that point would be a bigger historical achievement than President John F. Kennedy’s demonstration that a Roman Catholic could become president.

But as the campaign progresses, politicians, the media and the voters should take care that the old and discredited tensions over gender and race do not spoil what should be an inspiring show for the rest of the world of American democracy in action.