When he first ran for the Senate in 1972, Joseph R. Biden Jr. told the voters of Delaware in a radio spot: "Politicians have done such a job on the people that the people don't believe them anymore, and I'd like a shot at changing that."

Biden, the same brash, glib, charming, nervy figure who scored an upset at age 29 to become one of the two youngest men ever elected to the Senate, is now seeking the Democratic presidential nomination -- and suddenly finds himself in the dock of public opinion, accused of doing "a job" of his own.

Biden is under fire for using someone else's words as if they were his own in separate incidents spanning from his first year in law school 22 years ago to a stump speech he gave last month.

In one case, he was found to have lifted not just a highly personal speech passage but also the family tree of British Labor leader Neil Kinnock.

Biden told a debate audience in Iowa last month of his ancestors who had worked in the coal mines and had never gone to college. That was a literal description of Kinnock's lineage, but a loose caricature of his own. One of Biden's grandparents was a mining engineer; none was a miner. One ancestor had gone to college.

Biden's critics seized on the episode as evidence of intellectual sloppiness at best, shallowness of character at worst. Here, they said, was the ultimate political con: a candidate ready to repackage even his own grandparents.

To Biden and his supporters, the episode was bewilderingly overblown. They said his failure to attribute the Kinnock quote was an inadvertent lapse, his phrase-borrowing from other political figures is standard practice in the marketplace of political oratory and that the law school "mistake" grew from ignorance, not intent.

His defenders also argued that what sets Biden apart from other presidential candidates -- and what ultimately will enable him to ride out the storm of editorial cartoons and late-night monologues -- is his decent, well-meaning character.

Such sharply divergent views long have swirled around Biden. "Joe's the kind of guy, either you like him a lot or not at all," said Mike Gelacak, a law school classmate who is working on the campaign. "There's no in-between."

The Biden persona is a mix of disarming candor, chip-on-the-shoulder brashness, biting humor often turned inward and a penchant for engaging any and all around him in nonstop emotional bonding. He said early on that he was running for president as the candidate with "real heart" -- this to set him apart from Gary Hart -- then the front-runner -- whom he viewed as too much in the thrall of abstract ideas to meet the multiple job requirements at 1600 Pennsylvania Ave.

Biden's political appeal has always been that of the regular guy, full of regular-guy flaws yet yearning to reignite for himself and his country the public spiritedness he knew as a young man. His speeches are richly evocative (and according to revelations this week, sometimes word-for-word) of the Kennedys, Martin Luther King Jr. and social movements of the 1960s.

As a senator, however, he sometimes has rejected the governmental activism associated with that era, most notably in 1975 when he broke with his friends in the civil rights movement on school busing. He said it failed the "cardinal rule of common sense."

Since then, Biden, who stuttered as a child, has made his mark mainly on the Democratic rubber-chicken circuit. His basic speech for much of the past decade has scolded Democrats for being too wedded to special interests and "fossilized" policy prescriptions, and has inspired them with the crie de coeur that "just because they murdered our heroes does not mean that the dream does not still live buried in our broken hearts." It is not uncommon for eyes in his audience to glisten when he's done.

His record as a legislator has been much more tame. Although his 15 years seniority have made him -- at a still-youthful 44 -- chairman of the Senate Judiciary Committee and ranking Democrat on the Foreign Relations Committee, he has few legislative triumphs to his credit. Critics say what has been lacking is attention span and any prolonged, deep commitment to issues.

Biden thinks Washington underrates his discipline and tenacity because he has never tried to be an insider. But over the years he has fed this image as a skate-along-the-surface generalist -- often reveling in stories about his student days, with desperation all-nighters and bouts with nearly flunking out.

In the midst of the plagiarism controversy last week, Biden released his academic records. He finished 506th out of 688 at the University of Delaware and 76th in a class of 85 at Syracuse Law School. He had to repeat three law school courses, including the one he failed for lifting without attribution five pages of a published law review article and submitting it as his own. He said last week that he did not understand at the time how to write a legal paper and that the plagiarism was unintentional.

What he had, even then, were people skills. One Delaware professor wrote in Biden's file that he had spent "his first three years trying to be the complete 'Joe College' with the result that his academic record does not reflect his true ability."

"Joe has an ease with people, a charm with people, an ability to put himself in the other guy's shoes," said his sister, Valerie Biden Owens, who managed all of his Senate campaigns.

"He's forceful and forthright and straightforward," Gelacak said of Biden's political appeal.

Why, then, did he miscast his heritage?

"He has a peculiar ability, that most people don't, to honestly get wrapped up in his own emotions," Gelacak said. He added that Biden "was very affected by that Kinnock speech," which he viewed on video tape this summer. "When he uses it, he gets wrapped up in it.

"Those of us who have known him a long time sometimes find ourselves saying, 'Gee, I wish he hadn't said that,' " Gelacak continued. "But that's also what we find so attractive. This {is} one guy not afraid to express his visceral reaction."

Over the years, Biden often has found himself having to make amends for operating at the visceral level. The tendency was especially pronounced in his first term, when he was still reeling from the enormous tragedy that befell him six weeks after his 1972 election: His wife and infant daughter were killed in an automobile crash.

Fifteen years later, Biden is a far more disciplined politician, but some tendencies die hard. On the nomination of Robert H. Bork to the Supreme Court, he got himself in hot water first for saying he would vote to confirm and later that he wouldn't -- eventually saying that he wished he had held his tongue until he could present a detailed legal explanation of his views.

Assuming Biden stays in the presidential race, there could be more news conferences at which he admits error, explains what he meant to say -- as he did last week in the middle of the plagiarism controversy -- and asks the forbearance of a fair-minded public.

To his supporters, he does it well. "I was as proud of him after that press conference as I was when he walked me to school on the first day of first grade," said his sister, Valerie, who is three years younger than Biden. "Even prouder."