Have you heard the one about Sen. John McCain being old?
Maybe this one, from The Tonight Show With Jay Leno: "John McCain says he has a list of about 20 names of potential vice presidential candidates. I don't want to say John McCain is old, but the list begins 'Hear ye! Hear ye!' "
Ba da boom.
Since he announced his candidacy for president, there has been no shortage of jokes about the age of McCain, who turns 72 this month.
From late-night talk shows to blogs and Web sites, many observers find the Republican candidate's white hair, lumbering gait and grandfatherly disposition fodder for humorous discussion. Even McCain has joked about it.
But many experts on aging say the jokes aren't funny and are a sad reminder that older people are one of the few groups left in America that it's OK to publicly mock.
"People don't think that ageism is important like racism or sexism," said Ronni Bennett, 67, who writes a popular blog for seniors, "Time Goes By." "Just to say he's too old, based on the fact that he's 71 years old, it's unfair and wrong and ageist."
So what is ageism?
According to Dr. Robert Butler, president and CEO of the International Longevity Center, who coined the word in 1968, ageism is a form of stereotyping and discrimination against people simply because they're older. Experts disagree as to when "old age" officially begins, but many use age 60 or 65 as a marker.
In his book The Longevity Revolution, Butler writes that "ageism takes shape in stereotypes and myths, outright disdain and dislike, sarcasm and scorn, subtle avoidance, and discriminatory practices. ... Older persons are subject to physical, emotional, social, sexual and financial abuse. They are the focus of prejudice regarding their capacity for work and sexual intimacy."
He goes on to say that one of the most profound forms of age prejudice is when older people are denied the satisfaction of meaningful work.
Experts say it's too early to tell if age discrimination will hurt McCain come November. "The polls do show more people are concerned about his age than are concerned about Obama's race," said Allan J. Lichtman, a history professor at American University and author of The Keys to the White House. "It's definitely an issue."
Last month, an AP/Yahoo poll reported that when asked to pick a word that comes to mind in thinking of McCain, the most common response was "old" - as opposed to "change" for Obama, the presumptive Democratic nominee.
Publications including The New York Times have delved into the issue of age as it pertains to McCain's candidacy, as have Web sites such as The Huffington Post and Politico. In February, writer Anna Quindlen penned for Newsweek "How Old Is Too Old," in which she called age "the new taboo in a vitality culture."
One can buy a McCain T-shirt that reads "Old is the New Hope" or one that blares "McCain is Really Old" at a Web site of the same name. Other sites have emerged since McCain announced his candidacy, including "Things Younger than McCain," which lists "Howdy Doody" and "the flexible drinking straw."
And Leno and David Letterman nightly find jokes to fill their opening monologues. Both have cracked wise about McCain being forgetful, sleepy - or worse, near-death.
"I don't want to say that McCain looks old," Leno said during one show. "But when he tried to leave the funeral home, he had to show I.D."
"It seems almost every night there are ageist jokes," Bennett said. "What if you just substituted the word 'black' or 'a woman.' ... They'd be pulled off the air."
Dr. Bill Thomas, a professor at the University of Maryland, Baltimore County's Erickson School, which has a focus on aging, said the jokes are alarming, but not surprising.
He said many people view McCain as a 70-something rather than as an individual.
"Voters can ask questions and be critical of his positions and his candidacy, but to dismiss him out-of-hand because he's 71, soon to be 72, that's not acceptable," Thomas said.
Complicating the issue of McCain's age are concerns about his health. He is a three-time melanoma survivor who recently had a small patch of skin removed from his face and biopsied as part of a regular checkup with his dermatologist. He is also unable to completely raise his arms, though that infirmity is the result of injuries he suffered during the Vietnam War, not age.
But, "One of America's greatest presidents was not able to stand without being held upright," Thomas said of Franklin D. Roosevelt, the nation's 32nd president. "He was virtually paralyzed from the waist down from polio, and that did not in any way interfere with his ability to lead the nation."
For his part, McCain has taken most of the questions and joking in stride.
Early in his campaign, McCain responded to a voter's question about whether he worried he might die in office or develop Alzheimer's disease by good-naturedly calling the young man a "little jerk." His response garnered laughter from the audience, but Butler said such questions are misinformed.
"We had the same thing with Bob Dole, [who] was 73," Butler said of the former Kansas senator and 1996 Republican presidential nominee. "We got the same questions from the press: 'Can he do the job? Is he too old?' The truth is, if he'd been elected and re-elected, well, he's still alive years later, selling Viagra.
"It's a matter of function not a matter of age," Butler said.
Other political leaders have had to deal with questions of age.
"Remember when [Ronald] Reagan ran for re-election; he was 73," Thomas said. "So it's not that Americans won't vote for people in their 70s. But Reagan, if I may point out, appeared younger than his stated age, while John McCain appears older than his stated age."
But images of Ronald Reagan in his later years might contribute to McCain's problems, some experts said.
When he was inaugurated in January 1981, Reagan was more than two years younger than McCain would be if he wins the election and becomes president.
Still, Reagan's last term as president was marked with bouts of forgetfulness, and he later developed Alzheimer's disease.
Just last week, an Associated Press article listed in great detail some of McCain's gaffes - he's confused the names of Middle Eastern countries, for example, and referred to the Czech Republic as Czechoslovakia - and indirectly linked those mistakes to his growing caricature as an "old man."
But Thomas said such word-finding difficulty is a common and well-known feature of normal human aging.
"When people say, 'Oh, senior moment!' that almost always is a word-finding difficulty," he said. "It means nothing. It's totally benign, totally innocent."