In the Democratic primaries last winter, Sen. John Edwards came on with the effervescence of uncorked champagne: An easygoing, relentlessly cheerful man, who barely six years into his political career has fashioned a reputation as one of his generation's most skilled public performers.

Beneath the simple appeal of his performances, however, is a life story of uncommon complexity. Far from easygoing, Edwards has shown a drive and discipline that are notable even by the standards of his former career, as a trial lawyer, and his current one, as a first-term senator from North Carolina who now has a spot on the Democratic presidential ticket.

Edwards's sunny-side-up approach to campaigning -- which made a winning impression with voters but yielded only two actual wins in the nominating contest -- is entirely authentic, according to many people who have worked for and with him. But this cheerful exterior also obscures an ambition that was fueled in youth by resentment at the snobbery he saw aimed against his working-class father, and in middle age by the grief that flowed from the death of a beloved teenage son.

Sen. John F. Kerry's decision yesterday to summon Edwards, 51, as his running mate on the Democratic ticket this fall ensures that this arresting -- and in some places controversial -- biography will become well-known to Americans over the next four months. It also sets up one of the most vivid stylistic and substantive contrasts imaginable.

Edwards, whose Senate years have won him praise for being energetic and a quick study but produced modest legislative achievements, had just graduated from North Carolina State University when Richard B. Cheney first held a senior White House position, in 1974. With a smooth-spoken style and a mop of golden hair, Edwards represents an entirely different breed of politician than the gruff and bald vice president. The Democrat became a wealthy man by suing corporations. The Republican became a wealthy man by being chief executive of a major energy services corporation, and as vice president he represents an administration that disdains trial lawyers and has sought legislation to curb their influence.

Cheney did not bring conventional political assets to the campaign in 2000, but with a quarter-century of Washington experience in Congress and the executive branch, his value to President Bush was obvious once it came time to govern. With Edwards, the situation is reversed. He brings a dynamism and theatrical presence that many Democrats say Kerry lacks, but his governing credentials are far less substantial.

In the Senate, Edwards had signature issues. The most prominent was his effort, in which he joined forces with Republican Sen. John McCain (Ariz.), to craft "patients' rights" legislation allowing people to sue HMOs. The Senate forged a compromise among its members to pass a bill but never could reach agreement with the House over a competing version. He also had signature strengths, including an ability to rapidly distill complex issues and describe them in compelling human terms.

Mostly, though, Edwards has been known in Washington for an ability to impress audiences, and he put himself at the front of the political pack with extraordinary speed. This was exactly the trait that he first displayed in North Carolina.

When Edwards first decided to run for the Senate against Republican incumbent Lauch Faircloth in 1998, even his own mother did not quite grasp the reach of her son's ambition. As she recalled it last year to the News & Observer in Raleigh, N.C., Bobbie Edwards said, "That's great. So you are going to run for the state Senate."

"Oh, no, Mama," the candidate replied. "The U.S. Senate."

"He skipped all the lower rungs," said Ferrel Guillory, an analyst of southern politics at the University of North Carolina at Chapel Hill. In the primary, Edwards edged out a Democrat who initially had more backing from the party establishment, then went on to beat Faircloth by 4 percentage points. He did it by spending about $6 million of his own money and by striking the populist themes that were his mark earlier as a trial lawyer and later as a presidential candidate. "What we learned in 1998 was his ability to blend his personal skills and his biography and convert that into a policy message," Guillory said.

One of the most important parts of Edwards's biography is one he rarely speaks of publicly. It is the 1996 car accident that killed his 16-year-old son, Wade. Edwards and his wife, Elizabeth, whom he met at the University of North Carolina law school and married in 1977, refashioned their lives after this tragedy.

On the personal side, they decided to seek fertility treatments -- Elizabeth Edwards was then in her late forties -- to have two more children in addition to their daughter, Cate, who was then in high school. On the career side, Edwards decided soon after to plunge into politics. He displayed interest before, but it was episodic -- he did not vote in some elections in the late 1980s and early 1990s. Soon he was running for the U.S. Senate. Some friends say that the family tragedy was in some sense liberating -- an electoral defeat could hardly add to the sense of loss he already felt, while a victory could lend ennobling purpose to an otherwise incomprehensible loss.

"The one thing a child's death does is wipe the slate clean for you," Elizabeth Edwards told the Raleigh newspaper.

The self-confidence, and even impatience, with which Edwards pursued his ambitions long had been evident. Some of it may have come from a childhood that was never marked by deprivation, but was colored by a sense of class awareness. Edwards's father, Wallace, worked in a textile mill, since shuttered, in rural Robbins, N.C. "I knew how good a man he was and how much he cared about people around him," Edwards said in a Washington Post interview last year, recalling how shabbily his father was treated "because he didn't make so much money or because he did not have a high school degree."

Once, he said, they went to a fancy restaurant in their Sunday best after church, when his father abruptly announced they had to leave. The prices on the menu were unaffordable.

Edwards was the first person in his family to attend college. And all through his life he has shown a certain brass -- or, at the very least, an indifference to doubters -- in pursuing his ambitions. Some of this was evident even in yesterday's news. Although the choice of running mate was Kerry's alone, Edwards did everything he could within the unstated rules of the game to enhance his chances. After it became clear in early March that he was not going to win the nomination, Edwards stayed busy on the campaign trail by attending every Democratic fundraiser and unity event possible, trumpeting his former rival but also demonstrating his own appeal.

"It has all the earmarks of a very carefully planned campaign," said one longtime political adviser to Edwards. "I think he realized that the best thing he could do was to raise money for the Kerry campaign and the Democrats and thereby get people in the party and in Congress to lobby for him. There's nobody in the world better at selling himself than John Edwards. He's proven that over and over again. He set out to sell himself to John Kerry and, once again, he's succeeded."

Part of what sold Kerry, as the presumptive Democratic nominee himself described it yesterday, was Edwards's formidable skills as an advocate. Those skills are a product of the courtroom just as much as the campaign trail. And although they look natural -- and surely do come at least in part from intuition -- they are also a product of careful work and study.

Edwards is described as a well-prepared practitioner with instinctive people skills who can assess the salient points in a case and write his closing argument before the first deposition is taken.

"As I tell it, he's not the best person in the world at picking a jury, or the best closer or the best on cross [-examination]. But he does everything together really well," said Jim Cooney, who has tried more than a dozen cases against Edwards. "What separated him from everyone else is that he brought trials to a higher level. His greatest strength is that he had a real vision of all the pieces of the case and how they would work together. He knew the deficiencies of the other side before they did."

Edwards appealed to juries to win tens of millions of dollars in record judgments from manufacturers and hospitals for middle-class families. In one celebrated case, in 1985, in which a young girl had been brain-damaged at birth, he implored the jury in his closing argument: "She speaks to you. But now she speaks to you not through a fetal heart monitor strip; she speaks to you through me."

The jury awarded $6.5 million to the family, then a state record award for medical malpractice. It was reduced to $4.25 million on appeal.

"It's not that John woos juries. They don't like John -- they come to like the cases he presents," said Mark Kurdys, who was up against Edwards in one of his last cases before running for the Senate.

Edwards's legal career left him with a personal fortune with assets valued between $13 million and $38 million, according to his most recent Senate financial disclosure form, filed in May. One question awaiting the fall campaign is whether his legal career will be seen by more voters as evidence of his commitment to average people who have been treated unfairly, or as evidence of an out-of-control legal system that drives up insurance and health care costs.

A similar question about his short Senate career awaits resolution. Has he risen so fast because of extraordinary talents, or because of a self-promoting style that draws cameras but few concrete accomplishments?

When he arrived in 1999, he was immediately tagged by colleagues as a young man in a hurry -- welcomed by many Democrats as an articulate champion of some of their favorite causes but eyed suspiciously by Republicans and even some in his own party as callow and overly ambitious. After five years, these impressions remain largely the same.

"As soon as he came to the Senate, he became a star on the team . . . a center of gravity almost instantly," said Minority Leader Thomas A. Daschle (D-S.D.).

Said Sen. Tom Harkin (D-Iowa): "This guy's got boundless energy, and he's willing to put himself in the thick of things." On patient care, "he was able to use his skills to explain complicated things in a simple way . . . he brought real-life stories to the debate" from his own courtroom experience.

Edwards showed a keen interest in clean-air issues and led an effort in the Senate to block Bush administration efforts to relax the enforcement of industrial clean-air rules. In January 2001, an amendment he offered to delay the administration's relaxed rules for refineries and manufacturers was narrowly defeated, 50 to 46.

"Edwards personally lobbied members, and he vastly exceeded all expectations for how many votes he would round up," recalled Frank O'Donnell, executive director of the Clean Air Trust. "He did that by personal charm and personal lobbying, and he threw a real scare in the business community."

Republicans see the Edwards record far differently. "He was competent when he was here, but he was often missing," said Sen. Gordon Smith (R-Ore.). "His influence here has been fleeting. I always had the impression he began to move up before he even sat down in the Senate."

Staff writers David S. Broder, Helen Dewar, Eric Pianin, Lois Romano and John Wagner contributed to this report.

Sen. John Edwards arrives at the Pittsburgh airport with his family -- from left, his wife, Elizabeth, son Jack and daughters Emma Claire and Cate.Presidential hopeful John F. Kerry, left, and his running mate, John Edwards.