The great thing about the New Hampshire primary is the chance to do a stunt like this: in 12 hours, and about five bucks in tolls, see all four leading contenders for the White House in action.

Catch Bill Bradley at a convention of social workers. Watch John McCain address the New Hampshire legislature. Hear a marching band blare a welcome for George W. Bush. Witness a marathon Q&A session with Al Gore.

It's striking the way they mirror and contrast one another. The Democrats and the Republicans could be two sets of twins. Vice President Gore and former senator Bradley are a couple of high achievers attracted to the details of governance; they know about "weighted averages," "WIC levels," "holistic approaches" and the history of Belgian colonialism.

Texas Gov. Bush and Arizona Sen. McCain, by contrast, are two hell-raisers made good, cracking jokes and sketching their ideas with broad brushes. The key to fixing education, says Bush, is to "refuse to accept that certain people can't learn." McCain has basically the same outlook. "We have to stand up to a liberal education orthodoxy that has a Bart Simpson mentality: 'underachiever and proud of it.' "

Or are the true twins the insurgents, Bradley and McCain, the hero athlete and the hero pilot, each armored in virtue and bearing the flag of campaign finance reform. Bush and Gore could be brothers, too--striving sons of politically accomplished fathers; the favorites of the party apparatchiks; two men who, when things go bad, come out fighting.

The four candidates are putting on quite a show in New Hampshire, where Primary Day is Feb. 1. Both races are neck-and-neck; the voters seem genuinely torn as they size up their options.

"I'm very happy with this field," says Leslie Burns, a Republican from Bedford who likes some things about Bush, other things about McCain and still others about publisher Steve Forbes. "I just have to decide."

Snow fell on Thursday morning, and the road to Nashua was slick enough to play hockey. Winter has been strangely summery this year, but, finally, New Hampshire felt like New Hampshire.

At 8:30 a.m., Bradley stands before a friendly audience. Several hundred leaders of community action agencies and Head Start programs from around New England listen intently to the man who has made child poverty a centerpiece of his campaign.

"Now's the time to think big," Bradley says. The choice facing Democrats is "between a bold choice and a more timid choice." And so he talks about his health care plan, promising access for all, prescription drug benefits and a network of community health centers. Next comes an expansive anti-poverty program. Then a plan to register every handgun in every American home or business. "We're at a time when we need to have these larger ideas."

Bradley is running as the anti-pol, earnest in manner, unstained. But that doesn't mean he doesn't work a crowd. This audience is presumably liberal, so he tells multiple stories from his recent experience on an Iowa picket line. He spent less than an hour on the line, but he manages to sound like John L. Lewis.

"He certainly has a big agenda," says Sandra Ford, a social services administrator from Somerville, Mass. But Bradley is a bit too airy for some of his audience. Susan Durgy, who runs the welfare-to-work program in Northwood, N.H., praises Bradley's recognition "that everything is not rosy at this point." However, she adds: "He didn't explain how he was going to pay for it."

At 2 p.m., John McCain observes a ritual of New Hampshire campaigns--addressing the state legislature. McCain's at his best in town meetings, where he mixes the affability of Johnny Carson with the simple can-do of Audie Murphy. Still, the essence of his campaign can be found in his statehouse speech.

First, the halo of heroism. When McCain steps to the lectern, under the huge portrait of George Washington, he adjusts the microphones with oddly cocked, inflexible arms. After 20-some visits, and a best-selling book, people here know the story of those arms. Shattered when his plane was shot down over North Vietnam. Battered, wrenched and rebroken during torture sessions over more than five years. Today, he cannot comb his own hair.

Next, as always, comes a self-deprecating joke. "Oh Lord, help me to utter words that are tender and gentle," he says, quoting the Arizona statesman and wit Morris Udall, "for at some future time I may have to eat them."

The speech that follows is ringing, yet vague. He promises to appoint a Cabinet-level "reform czar," but gives no hint what that means. This, too, is pure McCain. Of the four top contenders, he has offered the fewest specifics, yet he has probably stirred the most people. "My purpose is to restore the people's sovereignty over government; to renew their pride in public service; to reform our public institutions . . . to reinvigorate our sense of national purpose and destiny," McCain declares, and the lawmakers jump to their feet for a rousing ovation.

Londonderry, 5:20 p.m. This should be friendly territory for George W. Bush. The towns of southern New Hampshire are home to the burghers of the Boston exurbs who can't abide Massachusetts taxes. Sure enough, just inside the door of the local high school, wearing a Bush button, is a well-coiffed woman in a full-length fur.

He is the best-funded, most-endorsed rookie presidential candidate in more than a century, but McCain's surge in New Hampshire has Bush a little worried, and it shows. The school cafeteria is packed on a lousy night. Bush is a ball of nervous energy--knees bent, arms thrusting and coaxing, voice rising almost to a shout.

Things must be good here, because the mere mention of tax cuts is not enough to get the crowd cheering. What they like is when Bush worries about the working poor; they applaud vigorously when he complains that a single mother making $22,000 is being penalized by the tax system. "It's not fair!" Bush exclaims. "It's a tollbooth on the road to the middle class, and I intend not only to reduce the fees but to knock the tollbooth down."

Question period: A young man asks about drug use; Bush fends it off. "You're making assumptions about me that aren't warranted." He spends more time demonstrating his foreign policy expertise. Asked about America's global role, he says: "This'll take a little while; I'm gonna strut around the world a little bit," then assess various key regions.

But it's not all defensive. A question about charter schools launches Bush on a rambling but passionate account of his education policies as governor. He claims great results from a simple idea--that every child must learn to read by the third grade. Midway through his aria, he apologizes for long-windedness. "You got me on my subject here."

Everyone present receives a copy of Bush's collected policy speeches, a 200-page, slick-bound, illustrated volume. It is a casual, but vivid, glimpse of the campaign's amazing resources.

Now it's after 9 p.m., at Temple Beth Jacob in Concord, and the reporters who have traveled all day with Gore are bleary-eyed, slumped or cradling their heads in their hands. The vice president is going strong.

A man in the audience has asked why money to prosecute Rwandan war criminals is tied up by the bureaucracy. That was about 12 minutes ago. Gore--having discussed the operating procedures of the Agency for International Development, having laid out his six-point matrix for analyzing the deployment of U.S. troops, having detailed his many labors to create an African crisis response plan, and having surveyed conflicts from Congo-Kinshasa to Burundi--is explaining the value of economic interdependence.

The vice president is very smooth. He looks relaxed in his sweater and blue blazer. The crowd is arranged in a circle, and he speaks through a tiny microphone clipped to his shirt. This is a Jewish audience, so he gives them a few words of Hebrew and a Jewish grandmother joke.

Gore has the air of a smart man who has prepared for this all his life. He has a lot to say about everything, and he says it all. School violence takes him from Internet filters to the biblical story of Cain and Abel. Health care takes him from the human genome map to the intricacies of HMO cost controls.

He has been attacking ever since last fall, when Bradley pulled even in New Hampshire. But not tonight. Tonight, he's generous with praise for Bradley "for the fact that he and I have been able to put health care back on the agenda."

Tonight, Gore's fighting in a different way--by showing that he'll go longer and try harder than the other guys. Elect me, he says nakedly, "and I will work my heart out." As if to prove it, he talks on, and on, into the night.

CAPTION: Sen. John McCain, above in Hooksett, N.H., has used the same broad-brush approach as rival George W. Bush.