The issue American voters are likely to hear more about as Election Day approaches is the one that gets worse for John McCain with every passing moment — his age.

Mr. McCain, who will turn 72 in August, is a quarter century older than his opponent, Barack Obama, who will be 47 that same month. The generational attack is ongoing. Last week, one of Mr. Obama’s foreign policy advisers, Susan Rice, labeled Mr. McCain as being “confused.” Back in May, when the campaigns sniped back and forth over the issue of whether Hamas had endorsed Mr. Obama, the Illinois senator suggested Mr. McCain might be “losing his bearings.”

Officially, Mr. Obama’s campaign team is denying any hint of ageism. Speaking to Politico.com, for example, Ms. Rice explained that her comments were directed specifically about Mr. McCain’s statements on Iraq.

Even with the denials, age is beginning to permeate the race. The easiest and less overtly objectionable form of this comes with a contrasting of the campaign styles of the two candidates. Mr. McCain’s campaign has largely stuck to traditional means of communication and fundraising; Mr. Obama has been revolutionary in harnessing the power of the Internet and social networking groups.

But the imagery and language involved in the discussion highlight Mr. McCain’s age. “It’s the difference between a horse and buggy and a NASA space ship,” a former Democratic campaign consultant and founder of PoliticsOnline, Phil Noble, told Politico.

A long post at the DailyKos.com last week took the idea to excess. Headlined “McCain and Technology, Building a Bridge to the Nineteenth Century,” the post depicted such apparatuses as a zeppelin, a telegraph, and a high-wheel bicycle.

Mr. McCain’s campaign isn’t saying much anymore on the issue. Responding to it too vocally can serve to fuel it. A key ally of Mr. McCain’s, Senator Lieberman, addressed it in on “Imus in the Morning” the other day. “You can agree with him or disagree with him. But don’t vote against him because of his age,” Mr. Lieberman said, citing Mr. McCain’s “energy” and “experience.”

It may not make sense for Mr. Obama’s supporters to continue to push the subject of Mr. McCain’s age. It makes some people, particularly older Americans, very angry. One of them, New York employment attorney Murray Schwartz, broke away from a meeting to talk about the subject of age discrimination. Mr. Schwartz is a 1949 graduate of Brooklyn Law School. Less than two years ago, Mr. Schwartz won a $2.5 million verdict in federal court for a plaintiff who claimed age discrimination.

The law protects workers from being discriminated against because of their age. The federal government, New York State, and New York City all have laws against it. The AARP has a section on its Web site devoted to “Age Discrimination at Work.”

“Age discrimination is an insidious, egregious disease,” Mr. Schwartz said. “Age should not be a factor in any employment decision that’s made. Not in hiring. Not in firing.”

What about a case when a person’s age is not specifically raised, but they are referred to as “confused” or some other description? “If that person came to see me, I would find out whether they were confused,” Mr. Schwartz said, noting that often “buzzwords” or code words that allude to a person’s age, but don’t mention it directly, circulate around the workplace. “No one ever passes around a memo.”

While Mr. Schwartz stuck to the law and didn’t want to get into politics, he did provide a general statement about age entering into the presidential race. “If someone is going to be ignored as a viable candidate because of age, besides it violating the law, it would be shameful,” he said. He added that many professionals, including lawyers, reach their peak in their later years. “Experience is a major component of everything.”

A political campaign isn’t a court of law. Expect everything — at least with regard to Mr. McCain — to be fair game come election time. There’s no jury. But age-based attacks could backfire.

Even with the upsurge in youthful interest in Mr. Obama, many American voters are elderly. Key swing states, such as Ohio, Pennsylvania, and, of course, Florida, have large numbers of senior voters. They won’t like it if they feel discarded like an old horse and buggy.

Mr. Gitell (gitell.com) is a contributing editor of The New York Sun.