Go back four decades or so in American history, and tell someone that in the early years of the 21st century a black man would be running for president with a realistic chance of winning, and we all know what the likely reaction would be, right?

There would be disbelief, for starters, and if you got past that, there would be astonishment, because a dark skin would ruin your prospects for a public career in most parts of the country back then, and, in some parts, might even keep you out of the voting booth.

That was hardly the worst of it, but then came massive, often inspired protest, court rulings requiring equal rights, passage of momentous legislation in Congress and endless soul-searching by millions upon millions.

A nation mired in prejudice — not just in the South but nationwide — began to rise out of that miserable muck, not all the way, obviously, but enough of the way that first one impossibility and then another became possible and often became fact until finally we get to Barack Obama and the very real possibility of his being elected president.

Whatever your political take on this man — whether you like him, dislike him or are indifferent to him — you have to be impressed that this country of ours has come so long a way from past racism that African forebears do not foreclose the chance of someone winning the highest office in the land. It's an extraordinary historic development worthy of praise and rejoicing, just as the question being asked by some — is Obama "black enough" to count as "black," or to win the loyalty of blacks? — is deserving of contempt.

Some of those posing this question in newspaper columns and other forums are themselves black, and it would hardly be amiss if all they were getting at were doubts not yet answered in their minds about Obama's competence or stance on issues. Just as racial identity should not occasion opposition, it should not occasion automatic favor. Ideally, what should matter for citizens is not whether a candidate is black or white, male or female, from this region or that or of one religion or another, but their judgment of whether the candidate's abilities, political values and overriding philosophy will serve the common good.

A few of the commentators — and, reportedly, many more — go beyond such considerations, however, saying Obama is not one of them and does not therefore win their following because his mother was white, his father was directly from Africa and his ancestors did not experience American slavery or taste the bitterness of the Jim Crow South. It's said he has not endured what many fellow blacks have, and it has been suggested by white and black writers that whites are quicker to embrace him as a presidential candidate than, say, Jesse Jackson, because he does not stir up a deep-down animus the way a black of Jackson's background does.