With the first votes just seven weeks away, Campaign 2000 has descended into the trenches.

On the Democratic side, Vice President Gore and rival Bill Bradley are trading near-daily insults, a dramatic turn from a campaign that, from Bradley's perspective at least, was to be fought on a higher and nobler plain. Act 2 of this contest has brought a Gore revival after a summer of discontent. Bradley's campaign style dictated the rhythms of the contest for months. Now Gore appears to be driving the pace in a still-close contest.

On the Republican side, Texas Gov. George W. Bush, after months of floating above the field, has been pulled down into the maw. He lost his lead in New Hampshire to Arizona Sen. John McCain and his aura of impregnability after a candidate debate Thursday in which his rivals, most notably Steve Forbes, began to pick away at his credentials. Bush's superior resources and personal campaign style remain his most effective weapons, but the question is, can he withstand an early loss or two?

The campaigns test competing theories of nomination politics and the impact of a decade or more of bitter, polarized, negative politics in both parties. Gore revels in the old game of attack and parry. Bradley hopes voters will penalize that approach and reward him for trying to resist it. Bush counts on the depth and breadth of a 50-state organization to smooth over any possible early bumps in the road. No match for Bush in cash or establishment support, McCain hopes to use four early states, beginning in New Hampshire, as a springboard past his principal rival--although history is against him.

Once again the compression of time is a major factor. The crowds in New Hampshire these days are of a size one expects just before the primary. The evening newscasts are chockablock with political commercials. "We're lousy with campaign ads," said Tom Rath, the Republican national committeeman from New Hampshire. "It feels like it's about an hour before the election."

Everything continues to happen earlier in this campaign cycle, including Gore's effort to mount a comeback even before losing a contest.

Bill Bradley may look back on his debate with Al Gore in Hanover, N.H., in late October as the last moment of innocence--or idealism--in the campaign of 2000. He may also look back on it with regret.

That night, Bradley did what politicians are told never to do. He refused to respond to a direct attack against the centerpiece of his candidacy for president, his health care plan. With the vice president aggressively questioning Bradley cost estimates, the former New Jersey senator shrugged rather than rebutted. "We each have our own experts," he said.

Until that moment, Bradley was the surprise story of the Democratic race. He had raised more money than expected, closed the gap in New Hampshire by Labor Day, put forward the Big Idea of Campaign 2000 with a health care plan designed to move the country toward universal coverage.

Gore stumbled and staggered, trying to get it right. Whatever he tried seemed not to work. His campaign staff changed. His campaign address changed. His clothes changed.

But somewhere in mid-fall, two things began to happen. The candidate grew more comfortable on the stump and his campaign team reconstituted itself into one intensively focused on defeating Bradley and winning the Democratic nomination. Gore challenged Bradley to weekly debates. He cut a television ad the night the Senate defeated the Comprehensive Test Ban Treaty. He aired other ads about himself. And then he discovered the Bradley health care plan.

The day after the Hanover debate, Gore's campaign unloaded: too costly, not as comprehensive as advertised, too stingy for many uninsured Americans, too dangerous in its call to end Medicaid and move the recipients into the world of private insurance. Bradley still resisted, but subtly, the tone and dynamic of the Democratic race began to change.

"Bradley wanted this to be a dialogue about bigger and grander things," said Geoff Garin, a Democratic pollster. "Gore is forcing him to fight more on the particulars."

"It's not as if he's landing a crushing blow," Garin added. "He's just changed the fight more to his advantage. Bradley needs to figure out how to get back to the center of the ring."

Gore's luck is that Bradley's rise came early. In the accelerated timetable of this odd campaign cycle, Bradley's success was clear five months before the first contests. Gore not only saw his own problems, but also had time to try to find his way back into the race.

Last week, Bradley stood up and said "enough," challenging Gore for what he said were malicious distortions of his health plan and accusing the vice president of attempting to "take a broken system and throw more money at it."

In New Hampshire on Tuesday, Bradley offered his sharpest rebuttal of Gore's criticism and set a new tone in the Democratic race that continued throughout the week. Day by day, the rivals traded accusations about their policies and strategies.

Bradley claimed in an interview Friday at The Washington Post that Gore's attacks have done little damage. But in New Hampshire, the escalation of Bradley's television buy suggested concern about the direction of the Democratic race, where the most recent poll, published in the Concord Monitor, showed Gore at 45 percent and Bradley at 43 percent.

Other campaigns tracking the television advertising dollars reported that Bradley had significantly increased advertising on Boston television stations. A strategist for one Republican said, "It tells me that they have data or something that shows them with real slippage."

Gore's campaign team expressed cautious optimism about the race. Asked who has momentum now in New Hampshire, a Gore adviser said, "We've clearly stopped theirs."

The vice president, as is the way with candidates, sounded more confident. Standing on a stage yesterday in Rochester, N.H., having received the long-awaited endorsement of Gov. Jeanne Shaheen, he declared, "There's no doubt in my mind . . . we're going to come in first in the first-in-the-nation primary and we're going to win the nomination."

John McCain and George Bush remain remarkably civil toward each other in comparison. When McCain was getting whacked around in Thursday's debate about his temper, Bush stood up for him. "He's a good man," Bush said. McCain, in turn, was the lone exception on a night when Bush's other rivals pointedly criticized him. McCain's jabs were indirect and subtler.

But in New Hampshire their competition is fierce, a contrast in style if not so much in substance. McCain has burrowed into New Hampshire. His campaign boasts that he has held hundreds of town meetings and answered thousands of questions, perhaps a slight exaggeration. Bush has traveled there less frequently and shaken plenty of hands but relied as much on television as on personal campaigning to carry his message. The contrasting styles have left the men virtually even in most recent polls.

Bush has undergone a subtle and perhaps unanticipated change as the GOP front-runner. When his candidacy was taking shape a year ago, his hope was to be the fresh face, the outsider, who would come to Washington and set a new tone that would quiet the bickering and get government working for people again.

That still may be his message if he fights a general election campaign against the sitting vice president. But as his bank account soared past $60 million and the support of governors and senators and House members and other party leaders piled up, he has become a de facto Washington insider.

Bush is now so enmeshed in a cocoon of money and endorsements that McCain has seized the mantle of change. In Thursday's debate, McCain, who has spent 17 years in Congress, said, "If I am president of the United States, things are going to be a lot different."

In at least one respect, Bush campaign advisers now echo the Gore camp of some months ago. They see McCain as no more significant a threat than Gore's team saw Bradley as a serious rival last summer.

Perhaps they are correct. Every day new e-mails emanate from Bush headquarters announcing new recruits who are building political organizations in every state in the country and certainly in all those that count from now to March 7. Bush is prepared to compete everywhere, his advisers claim. Can McCain?

"Bush and Gore have locked up endorsements of governors, senators, congressmen, anybody with organizations in these other states," said Andy Smith of the University of New Hampshire. "That's the kind of infrastructure that's really hard to beat."

A Bush strategist said, "The big picture is there are only two states where McCain is close, his home state and New Hampshire. There's no other state where he's within 30 points. That's not how you win the nomination. It never works."

Polls can change quickly depending on New Hampshire's results. "Unexpected winners often get an extraordinary bounce from this primary," Emmett H. Buell Jr. of Denison University writes in a new book about the primary process. "Whether it propels them to win is another matter."

That presents two problems for McCain. Given his progress to date, a McCain win in New Hampshire would not represent a political earthquake. And even if he gets the traditional bounce, as Buell notes, victory in New Hampshire by an underdog is no guarantee of ultimate success.

McCain supporters count on what Marshall Wittmann of the Heritage Foundation calls "the Hindenburg effect" of a Bush loss in New Hampshire: "Once a dirigible loses altitude, it's difficult for it to be sustained."

McCain strategist Mike Murphy said his underfunded candidate should have enough money to compete effectively in key primaries that follow New Hampshire, but cautions, "We do need a New Hampshire bounce, sure we do."

Bush and McCain face different challenges. After what one GOP strategist calls "an incredible 90 days," McCain must sustain his momentum and fill out a profile that until now has been based largely on a maverick personality and a pledge to turn Washington upside down. Bush must put bite and energy into his appeal, rather than urging voters to listen to the voters in Texas.

Rob Ruback, a Concord lawyer who jumped from Bush to McCain last week, said the Texas governor must show more than he has so far. "He was reelected by acclamation," Ruback said. "He's popular with a wide cross section of voters, has a great deal of personal charm, which is increasingly rare in the Republican Party. But that's not enough. There's got to be more to it than that."

Bush also faces steadily escalating attacks from Steve Forbes, whose endorsement by the Manchester (N.H.) Union Leader may give him a boost to go along with the grass-roots organization he has been attempting to build in Iowa.

For all these candidates, there will be little rest in the weeks ahead. Republicans debate again on Monday in Arizona and then on Dec. 13 in Iowa. Democrats square off in New Hampshire on Dec. 17 and again on Dec. 19.

Christmas and New Year's lie ahead as a brief respite, but the holidays will pass in a blur as the candidates prepare for a stretch of campaigning in January that could prove decisive in both nomination battles--or set the stage for more protracted and bitter contests.