The Iowa countryside rolls by in a blur, but Bill Bradley, squeezed into a back seat of his campaign van, is sharply focused.

He is rising in the polls against Vice President Gore on what he calls his "joyous journey" in pursuit of the Democratic presidential nomination. His success, particularly in states such as New Hampshire, has made him a target of attack from Gore and his supporters. Bradley is unmoved.

"This is what I call dartboard politics," he says dismissively. "Throw a little dart and hope that it will be a poison dart. I think the people are fed up with that. . . . I'm not in the business of responding to every one of their darts."

Bradley's approach defies conventional political strategy, which holds that any attack must be met with a quick response. But it is a measure of the immense confidence he has in himself and his belief that, in this campaign, he -- not the vice president -- is in touch with the pulse of the people.

So far, Bradley's strategy has paid off handsomely by turning what many had predicted would be an easy race for Gore into a fierce contest. Ignored by the vice president, underestimated by many political analysts and a decided underdog at the beginning of the campaign, Bradley has risen by remaining steady in his course. In response, Gore has shaken up his campaign team, moved his headquarters, changed his clothes and stepped up his attacks on Bradley.

More difficult days lie ahead. Bradley has campaigned in relative obscurity for 10 months. Now in the limelight of his emergence as a serious rival to Gore, the voters will take a new measure of him.

Will he hold up as a high-minded candidate who is trying to change what he called a broken system when he left the Senate in 1996? Or will he be seen as just another politician who has changed his position on some issues like subsidies for ethanol (which are important in Iowa and which he now supports) and gone wobbly on his party on crucial fights?

And can a man who has the support of upscale Democrats and political independents win the hearts and minds of the party's rank-and-file voters who will determine the outcome of the nomination?

His campaign is the opposite of slick. The candidate's standard outfit on his weekend trip to Iowa consisted of a gray suit, white shirt that was supposed to be averse to wrinkles but wasn't, and a maroon tie mended with tape.

Knocking on doors in Des Moines Saturday morning, he loped from house to house, carrying himself with a slight slouch and occasional bemusement. "I'm glad that doesn't affect your going to caucus," he told Jack Ward, 64, after Ward pronounced Walt Frazier and not Bradley as his favorite New York Knick.

The candidate himself is consciously serious and sometimes cerebral, eschewing the traditional political oratory for a conversational tone. Despite his aversion to dartboard politics, he is not hesitant, when asked, to draw distinctions with Gore. His rival, he tells audiences, is "timid" and "cautious."

Wherever he appears, Bradley draws devoted followers whose accolades should make any candidate blush. When Bradley arrived at Iowa State University Thursday night, Nick Paindiras and several of his buddies were there to greet him, having come from Connecticut to spend the weekend in Iowa. Paindiras was holding a sign with the definition of the word "integrity." Under synonyms, it read: "Bill Bradley."

"I think America needs to refresh its soul, and Bill Bradley can do that," said Paindiras, a lawyer. "I think Bill Bradley's the real thing. He's not aspiring to be, he is."

John Tapscott, who introduced Bradley Friday afternoon on a farm south of Des Moines, said he hasn't been as excited about a candidate in 30 years. "This man comes along and he brings back memories of the Roosevelt-Truman days," Tapscott said. "I see him as the old Democratic principles."

Tapscott's view conflicts with that of Gore, who criticized Bradley Saturday night before 3,000 activists at an Iowa Democratic Party dinner. Gore accused the former New Jersey senator of being a disloyal Democrat.

Gore attacked Bradley for supporting President Ronald Reagan's spending cuts in 1981 and for quitting the Senate shortly after Newt Gingrich led the Republicans to power in Congress in the mid-1990s.

Gore said the better choice would have been to "stay and fight," and his supporters waved placards with the slogan. Bradley even mouthed "stay and fight" along with the crowd as Gore spoke, but he didn't look happy about it.

On stage, speaking before Gore, he had emphasized his Democratic credentials, hoping to inoculate himself. "There was no doubt in my mind," he said of the moment he decided to side with the party when Democrats led the fight for the Civil Rights Act of 1964. "I was a Democrat."

And he resisted answering Gore's anticipated attacks, calling instead for a campaign that would focus on the positive, not the negative. "It takes discipline to be positive," he said, "because it's easy to slip the other way."

In an interview he was even more insistent that Gore's attacks will not work. Asked about the debate over Reaganomics, he laughed. "What year was that? The poison on that dart -- are you sure the poison is still there after all those years?"

He may have voted for Reagan's spending cuts, Bradley says, but he was also one of eight Democrats who voted against Reagan's tax cuts. "I was the point man against Reaganomics, against the tax bill," he explained. "I was the only person on the Senate Finance Committee to vote against the tax cut. So what was I there? Was I standing up for Democratic principles? I would say so."

"If everybody had voted as I did, which was against the tax bill and for the spending cuts, there would have been no deficits in the 1980s," he added insistently. "Therefore all of the things we care about . . . would have been more possible, not less possible."

As for quitting the Senate, Bradley said the criticism might be more valid if he had not worked so hard to help elect a Democratic successor to his seat. "The votes in the United States Senate are virtually no different if I was there," he said. "I just don't buy that argument."

Mary Wiberg, an undecided Democrat, agreed. She was at the Saturday dinner and had seen Bradley in Ames on Thursday. "I think he was blowing something out of proportion a bit there," she said of Gore. "It wasn't something that resonated with me at all, that Bill Bradley had been less loyal than Al Gore or less `stay-and-fight' than Al Gore."

Other Democrats who heard Bradley this weekend said they continued to have reservations.

Nancy Lynch, a social worker for the Des Moines public schools, arrived at a backyard get-together with the candidate leaning toward Bradley. But after listening to Bradley explain his support for limited school vouchers when he was a senator, Lynch expressed doubt. "I didn't like it as well as I would like," she said. "Gore is stronger on that issue."

Bradley defended his past votes, and in an interview insisted that those votes have nothing in common with Republican Texas Gov. George W. Bush's endorsement of a federal school voucher plan. "There is a vast difference between what I've said on vouchers and what Governor Bush says on vouchers."

Gore taunted Bradley on Saturday night to debate him. Asked earlier why he had rejected Gore's challenge, Bradley said, "I haven't said I won't debate this year," adding that he would not "lay all the cards out on the table" about his strategy just because the vice president is calling.

Gore, he said, continues to enjoy all the advantages of an incumbent vice president: the support of President Clinton, control of the Democratic National Committee, key party fund-raisers, the aura of Air Force Two, the lead in national polls. But in dismissing Gore's claim to underdog status, Bradley framed the race in a way that cast himself as he would like to be seen.

"You have, in other words, entrenched power at your beckoning," he said of his opponent. "I've only got the people."