We live in a euphemistic age where, in the name of smoothing the rough edges of an often cruel society, it is considered poor form to mention someone’s gender (if a woman), or height (if short), or hair (if bald), or skin color (if it is other than white). It is not acceptable in polite company to mention that someone is “old.” Instead they must be described as “older.”

Once when I pointed out that middle aged people like me do not expect important announcements from an employer concerning health care to be sent solely by email, I was told that it was not because I was too old but that I was suffering a “generational” difference. Only after the conversation ended did I realize that for daring to describe myself as old had I been quietly but firmly reprimanded and patronized.

The intention behind the strictures against using plain language is a good one: to ensure that no one in this multi-cultural society is made to feel awkward or put upon for aspects of themselves that are beyond their control. The penalty for those who ignore this code of self-censorship is at best a silent reproof, at worst a full blown rant from a member of the self appointed thought police.

Except, it seems, in the presidential race. Two of the aspects of Senators McCain and Obama that will cause them to lose votes in November is, respectively, their age and their ancestry.

It may be neither fair nor pleasant, but, human nature being what it is, some will not back Mr. McCain because he is thought to be too old, some will not vote for Mr. Obama because he is black.

Such are our heightened sensibilities about avoiding offense that even those who draw attention to these rudimentary psephological facts are likely to be labeled ageist or racist.

But there is a double standard in operation. Of the two sins, racism is by far the more deadly. Color is strictly off limits while a person’s age, it seems, is fair game for humor.

How else to explain this joke from the politically adept Jay Leno, host of the “Tonight Show”? “Democratic operatives have been looking for dirt on John McCain. You know what you call someone who digs up dirt on John McCain? An archaeologist.” Or this: “Last night we had Cindy McCain on and she talked about her favorite antique, her husband.”

Then there is “Late Show” Host David Letterman: “John McCain looks like a guy whose head you can barely see over the steering wheel. John McCain looks like the guy who thinks the nurses are stealing his stuff.” Or Mr. Letterman on the pope’s visit: “The pope, after the mass, accidentally gave the last rites to John McCain.”

And Late Night Host Conan O’Brien: “John McCain is having trouble raising enough money for his campaign. Plus, every time someone does donate money to McCain, he puts it in a card and sends it to his grandchildren.” And “Late Late Show” Host Craig Ferguson: “John McCain admitted today he didn’t vote for George W. Bush. He did, however, vote for George Washington.” And so on.

Sifting through the late night monologues since the primaries began, I could not find a single racist joke. Race and age are the great subterranean themes that are at play in the presidential election and are at least as potent as the differences between the rival candidates over issues such as health care and free trade.

There is high anxiety among many Democrats about Mr. Obama as a candidate, and quiet glee among Republicans, because they know that racism will be an important factor in the general election. How important the race factor will be is hard to gauge. Polling on race is notoriously difficult because respondents cannot bring themselves to admit that race will influence their vote, even in an anonymous survey to a faceless pollster over the telephone. But the results do show that race matters.

A Newsweek poll taken between April 24 and April 25 asked voters whether America is ready for an African-American president, and 19% said no, with 7% saying they were unsure. That is more than a quarter of the electorate.

A subsidiary question was worded to test the true feelings of respondents. It asked whether those who said America was ready for an African-American president held views about voting for a black candidate they were not willing to express. More than half, 53%, said they believed that “most” (12%) or “some” (41%) of the 74% saying America was ready for a black president were disguising their real thoughts.

Little wonder that many registered Democrats who have voted for Senator Clinton — and they are almost the same number as those who have voted for Mr. Obama — believe Mr. Obama is likely to lose in November because he is black. When Mrs. Clinton said as much in West Virginia this week she was pilloried by Mr. Obama’s supporters for “playing the race card.”

Although Mr. McCain may appear to be at a disadvantage because his perceived weakness is regurgitated and reinforced nightly by entertainers who ridicule him because of his age, Mr. Obama ultimately may suffer the most because his disadvantage is not spoken about openly.

Mr. McCain can address the issue of age head on. He can point out that the very notion of age is fast changing. Sixty is the new 40 and 80 the new 60.

Mr. Obama, meanwhile, dare not raise the issue that, like an iceberg, threatens to sink his chances. Truly, it is no laughing matter.

nwapshott@nysun.com