"Thank you, Jenna, for that very sweet introduction. One of the great things about having the girls on the campaign trail with us now is getting to hear them talk about how much they love us -- and in public, no less."

-- First lady Laura Bush, campaigning in Maine

Hey, would you look at all these kids! And don't they seem like such nice young people?

These guys must have done something right in their lives, huh?

They're popping up everywhere, the children of the candidates, all on a tear during a tight race. Not since all those well-scrubbed young Kennedys have so many kids been pressed into service in such high-profile fashion.

There are the Kerry sisters, so brainy they're intimidating, hitting college campuses, giving interviews. The Bush twins, the sassy ones with the swivel hips, introduce Mom or Dad, thank volunteers, giggle to each other when the boys at the rallies hoist those Bush-Cheney '04 signs with their phone numbers scrawled on the bottom. They have their own blog, Jenna and Barbara do, heavy on the word "awesome," and sometimes they take a turn in the phone bank. Imagine the response that can provoke: Dude, I came home from the bar and one of those Bush girls was purring into the answering machine, thanking me for all my hard work.

Even two of the stepsons, those handsome Heinz boys, have put their careers on hold to stump for their stepdad. Chris, the former banker, speaks up on economic policy. Andre, the greenie consultant, breezes through environmental issues.

After the vice presidential debate, the network pundits can't wait to patter, but blessed C-SPAN keeps its camera on the stage, and here's the whole fascinating family dynamic on display: Liz Cheney, lawyer and former State Department heavyweight, capable of arguing eloquently for democracy in oppressed nations and cradling her fourth baby at the same time! Her sister, Mary, the one John Edwards has just reminded 43 million viewers is a lesbian, with her partner, Heather Poe, who once managed their ice hockey team. Cate Edwards, like Jenna and Barbara a recent college grad, grown so polished she can spout on CNN like a paid operative, but bummed she has to trade in flip-flops for big-girl slingbacks. Her little sibs, Jack and Emma Claire, score their points as adorable towheads, being hoisted from one hip to the other. In a bewildering crowd, it's comforting to be in Daddy's or Mommy's arms, and it has a neat strategic effect: The kid stays in the picture.

In presidential politics, children of the candidates come in only two sizes: big and little. Middle-sized ones are too awkward for political utilization.

The little ones are pure bundles of unscripted joy. Emblems of their parents' youth and vitality and procreativity, they're cute even when misbehaving. Little ones haven't wrecked the car yet, aren't on Ritalin yet. We haven't seen little ones like the Edwards kids in a long time, not since John-John peeked out from under the Oval Office desk to tell us we were all about the future.

The big ones are potentially more useful, but so much more complicated. Take Mary Cheney, who is 35. Her father's top aide on the campaign, she has managed to stay nearly invisible and silent through two campaigns, but when John Kerry also mentions that she is a lesbian, President Bush and both her parents feel the need to rush to her aid. The ensuing flap becomes big political news. Her life story takes on a life of its own.

Why, exactly, are these kids out there? What are they trying to tell us, and why do we care?

"It's fairly simple," says John Dukakis, who stumped steadily when his stepfather, Michael Dukakis, ran for president in 1988. "Part 1 is the ability to share the message, to reinforce what your father is doing. And Part 2 has to do with associating the candidate with a more human side. I guess to the extent that we are reflections of our parents, it's a chance for people to feel like they have a better idea about this person as a human being."

Both the Bush and Kerry daughters have had their prime-time moments talking about their fathers at the conventions. Both have had their glossy rollouts in Vogue, a spread that served as a coming-out for the previously sheltered president's girls. Appearing together, the sister acts also made a pitch for voting at the Video Music Awards. The combined Kerry-Edwards crew has made hundreds of appearances and print, radio and television interviews, according to Stephen Gaskill, chief of staff for the Kerry and Edwards families.

"Candidates are controlled, every word and facial gesture," says Doug Wead, author of "All the Presidents' Children," a history that grew out of research he did for George W. Bush after his father won the presidency in 1988. "Kids are a weak link. . . . One can pick up clues from the kids."

Chips Off the Old Bloc

So what's he really like, huh?

Vanessa Kerry, 27, wearing a flirty, pop-arty top and tight jeans, is speaking to a bunch of young Democrats at the University of Pennsylvania before the first presidential debate. It's her fourth college rally of the day. A graduate of Yale, like her dad and Bush, and on leave from Harvard Medical School, she is now enrolled in a global health course at the London School of Economics, which requires her to take classes there Mondays through Wednesdays. Most weeks she jets home, flying coach on Wednesday nights to campaign until Sunday, when she flies back to England.

Unlike her father, she can pull off the don't-hate-me-because-I'm-smart routine. She recalls how her father was onto her when she was about to head out partying. "He wanted to know where you were and what you were doing," and her audience chuckles knowingly. "And that kind of demanding of the truth is what I see" as he runs for president. "That is what this election is about for him" -- finding the truth. "It's not about him, or his campaign," Vanessa says, but about "everybody in this room and everybody in this country who wants to know they have a president who is fighting for them and investing in the country."

Talking rapidly, pacing the front of the room in high-heeled sandals, she ably fields questions about getting out the rural and Hispanic vote, about Kerry's positions on protecting Israel and engagement in Sudan. Then a young man cuts to the chase. He wants inside information on the debate. "What did your dad say? What are we going to see? What's the preview?" The young Dems sit up in their chairs, eager for her answer.

"I talked to him today, yeah," says Vanessa. "He said, 'I love you, I gotta go, bye.' " Not much there, but everybody gets the situation, and they all crack up.

Later that night, during an interview, wolfing down takeout Thai food, she apologizes several times for eating and talking at the same time. Her job, she says, is to reveal John Kerry the father, the man who separated from his first wife, Julia Thorne, when Vanessa was 6 and her sister, Alex, was 9. Running for president, especially for someone with a reputation for being aloof, requires one to put the ordinariness of daily life in a display box, like a perfectly lighted collectible. So we have been given to know this: Most weekends, the single senator left Washington to be with his daughters back in Boston. He helped them with their homework long-distance. It wasn't a sacrifice, he told Dr. Phil, but "the most important thing that you can do."

"People look to me to see what kind of dad he is," Vanessa says. "But I get a lot of policy questions. I find myself having to really talk about the issues, to debate them. I got policy-briefed before I went on the road. If I don't have the answer, I find that immensely frustrating." So John Kerry is the kind of dad who has a daughter just like him.

To her, this is fun. "People want to know who I am because it will reflect on my dad, and that's where I'm most comfortable, actually. It's when the conversation turns to me, like it sort of is right now, that I get a little less comfortable. I don't really know what to do with that."

There was a time she put a different name tag on her scrubs when making hospital rounds, because she no longer was Vanessa Kerry, medical student, but Vanessa Kerry, candidate surrogate.

That compartmentalization is hard "because other people will paint their ideas or concepts or hopes or desires on you, and you are always a public person, and you are always representing your father, by last name."

In the Fishbowl

This brings us to Jenna Bush. Earlier this summer, about to make a campaign trip with her father, she sat in the limo looking out at the press photographers -- and stuck out her tongue. John Kerry is not the only presidential candidate to have a daughter just like him. On "Dr. Phil," the president explained how he schooled his impish child on political protocol: "I said, 'Jenna, you just made national news.' I said, 'You've got to be more careful. You're in a fishbowl, and whether you like it or not, every move you make, particularly when you're with me, will be recorded.' And I think she felt terrible about it."

Candidates display their children the way people put pictures of their kids on their desks and trumpet their honor student offspring on minivan bumpers. And we eat it up, which means you can always book a kid on TV. "Frankly, if you go to 'Inside Politics' and tell them, 'I have so-and-so,' that's not half as interesting as saying, 'I've got his daughter,' " says Marla Romash, a former aide to both Al Gore and Teresa Heinz Kerry. Five of the Kerry, Heinz and Edwards kids have done the morning shows in a group, learning how to let each other talk. The Bush daughters have done interviews only twice, but the campaign has learned to publicize their appearances as photo ops, and all the cameras come running.

We notice the candidates' kids when they show up. They launch a thousand conversations: Why is Teresa Heinz Kerry grabbing little Jack Edwards's thumb out of his mouth in the photo op? Do those stepkids get along? Do they all crack up or find annoying the irrepressible Andre Heinz, 34, who once changed clothes on the campaign plane in full view of staff and a reporter. ("I'm wearing boxers!" he said in his defense, while his mother shrugged, trying in vain to shield him from view.) We notice when they don't show up. Why did Mary Cheney flee the vice presidential box at the convention right after Dad's acceptance speech? Why didn't she get up there onstage? Her very absence stirred up a hornet's nest of Internet blogging. Chris Barron, political director of Log Cabin Republicans, said members of the party "have created a hostile environment in which Mary Cheney was either unwanted or uncomfortable on stage with her family." Mary herself never speaks publicly, and no one at the campaign ever speaks for her.

Kids remain a rare opportunity for opponents to acknowledge a shared humanity. In the first presidential debate, Bush halted his scowls for a minute to praise the senator as a father. "I admire the fact that he is a great dad," Bush said. "Appreciate the fact that his daughters have been so kind to my daughters and -- in a -- what has been a pretty hard experience for, I guess, young girls seeing their dads out there campaigning."

Softening at this, Kerry thanked the president, adding, "I think only if you've -- if you're doing this, and he's done it more than I have in terms of the presidency, can you begin to get a sense of what it means to your families, and it's tough. And so I acknowledge the -- his daughters. I've watched them. I've chuckled a few times at some of their comments."

"I'm trying to put a leash on them," the president said, laughing. Kerry, chuckling, said, "Well, I don't know. I've learned not to do that, Mr. President."

Children offer different things to different candidates. The Gore girls were all blond earnestness. Chelsea Clinton gave her parents a sense that part of their life might be normal after all. After her father, the man who tried to build a bridge to the 21st century, nearly burned his bridge to his own wife, there is Chelsea in a famous photo, walking across the White House lawn hand in hand with Mom and Dad, linking them back together.

The Bush twins, in their expensive James Jeans and fashionista tops, are out there to make it hip to be a young Republican, Barbara telling People magazine that, faced with the hypothetical choice of Dad's big speech or the season finale of "The O.C.," "we can TiVo 'The O.C.' " At the University of Maine, criticizing how strategists ignore the potential of young voters, she said: "They think they don't have time to keep track of big issues when we have to keep track of what's going on in Us Weekly and MTV. The fact is young Americans do care about the kind of country we're building for our future." Or, to put it another way, those still Finding Themselves have the right to vote, too.

The twins offer a sense of giddy unstoppability. Didn't they give themselves a total pass in front of the nation, with that convention speech explaining past indiscretions with "When we were young and irresponsible, we were young and irresponsible"?

Once the tsk-tsks subsided, Bush campaign types let it be known that the girls were not such a terrible twosome at all. "The focus groups loved them," a strategist told U.S. News & World Report. "They weren't talking to you and me," said another. "They were talking to their tribe."

Other tribes sometimes talk back. When the Bush daughters hit a young Republicans' bash at a Boston bar, protesters picketed outside. Earlier this month, when the twins tore into New Mexico, the Democratic Party greeted them with a news release that read, in part, "all we ask of Jenna is that if she finds herself before her dad (preferably at a moment when the cactus juice has sufficiently liberated her from her inhibitions) that she remind him of the 414,000 New Mexicans without health care, that college tuition costs are up 35 percent, and that new jobs pay less."

"They don't have to know the briefing book. No one expects the children of the Bushes to stand up and recite why their dad opposes stem cell research," says Paul Costello, a former aide to Rosalynn Carter and Kitty Dukakis. "They are there to show that their father has raised them well, and to be a mirror of the family."

And, suggests Doug Wead, the campaign trail is a rite of passage for a Bush kid. In his book, he recounts a conversation he had with Bush when he was Texas governor. Bush said he would not run for president "because of my girls. They would be in college then and it would ruin their lives."

"Did it ruin your life?" Wead asked, referring to when Bush's father became president.

"No," Bush answered. "It made my life."

In the movies, presidential children are wise beyond their years. They solve diplomatic crises and give widowed Dad advice on how to woo the super-nice lobbyist lady and finesse social policy. They become their parents' peers.

In real life, a candidate's kids stay the candidate's kids forever. After Nov. 2, one set of them will face the crushing disappointment of defeat. They will fight the instinct to blame themselves, predicts John Dukakis, who now is a music mogul in Los Angeles, running Will Smith's Overbrook Entertainment. "It's exhausting, it's exhilarating," he says. "You are running on adrenaline for a year and a half. It's an experience I wouldn't trade for anything, and I would never want to do it again."

Jenna, left, and Barbara Bush yesterday in Henderson, Nev. When candidates' children campaign, it can show "that their father has raised them well," says Paul Costello, a former aide to Rosalynn Carter.First daughter Jenna Bush posed with W-shirted Jennifer Tucker at a campaign event last week in Independence, Mo. Left, Vanessa and Alexandra Kerry (dark hair) at the MTV Music Video Awards in August. The siblings have been highly visible campaigners for their father.