In "Citizen Mike" -- an Orson Welles-style video spoof made for a 1999 testimonial dinner and narrated by the likes of Peter Jennings, Donald Trump, Liz Smith, Beverly Sills, Christo, and Percy Sutton -- the life story of Bloomberg, from lowly number cruncher to William Randolph Hearst-like media maven, is treated with amusing irreverence. The omniscient narrator intones at the Citizen Kane-style beginning, as a baby picture flits by on the screen, "The momentous arrival of Michael Rubens Bloomberg goes somewhat unnoticed on that fatal natal day. He will make them pay for that."

Bloomberg's father was a bookkeeper for a dairy who died of heart failure in 1963. After his death, Bloomberg's mother, Charlotte, went to work as a secretary. His parents were never all that consumed with material success, he says, adding that his 92-year-old mother has refused his offers to treat her to a nicer home, preferring to stay in the family split-level in Medford that Bloomberg's parents bought for $11,000 some 50 years ago. Mom, in fact, is still so independent that when she uses a car service at night that's billed to her son, "she sends me a check!" the billionaire says with incredulity. "It drives me crazy."

At Johns Hopkins, Bloomberg was the first Jew to join the Phi Kappa Psi fraternity. John Galotto, a Maryland internist who was one of Bloomberg's frat brothers and remains a close friend, recalls, "When we were rushing him, I looked into his closet and there was this chart his mother had made for him of what shirt to wear with what suit." Bloomberg, an engineering major, became president of the fraternity, even while holding a job as a parking attendant at the faculty club to pay his living expenses. "I wasn't smart enough for a scholarship," says Bloomberg, who took out college loans. Galotto adds that Bloomberg was driven to succeed: "He wanted people to think that everything came naturally, but you'd see him at 2 a.m., dragging 50 feet of paper home from the computer lab." (These days, Bloomberg the student is studying Spanish for the campaign trail, although he ruefully admits that languages aren't his forte.)

Accepted at Harvard Business School despite mediocre grades -- "I bet they're thanking their lucky stars that some admissions officer let me in," says Bloomberg, alluding to his hefty donations to his alma mater -- he expected to go to Vietnam upon graduation but was turned down after his Army physical revealed that he had flat feet. So instead he moved to New York in 1966 and joined Salomon Brothers as a trainee.

What Bloomberg discovered at Salomon Brothers was that he loved to sell, to close the big deal, to hustle stocks and bonds to institutional customers, to feel the adrenaline rush on the trading floor. America has always had a weakness for really talented salesmen. And though he may be a novice politician, he's been prepping for decades for the handshake-and-a-smile rigors of a campaign in which the only difference, this time, is that the product will be himself. "A good salesman never gets discouraged," says Bloomberg, who doesn't seem to have ever had a Willy Loman day in his life. "Sometimes people say no," he says, "but what's great about sales is that you know whether or not you're connecting and convincing people."

"He's a bawdy guy, very funny, but you don't take 75 percent of what he says seriously; he just loves to get a rise out of women."

In 1979, after a power struggle, he was transferred away from Salomon's trading area to a dead-end job upgrading and running the firm's computer operations. Two years later, when Salomon Brothers merged with the Phibro Corp., Bloomberg was among a number of partners who were let go; but he received $10 million as his share of the sale. "What's amazing, in hindsight, is that the firm let him go because they saw no value in what he was doing," says Richard Grand-Jean, a former Salomon partner who now runs his own firm. Bloomberg's 1997 autobiography, Bloomberg by Bloomberg, gives a breathless account of what happened next: how he started his own company and built the ultimate futuristic financial-data machine, with every possible stock and bond and commodities price, and computer software to twist and turn the numbers into five-year charts and comparative returns. With a mere idea of a product and the best sales pitch of his life, Bloomberg won Merrill Lynch as his first customer and major investor (the firm still owns 20 percent of his company). In twenty years, he's created a financial colossus: Bloomberg's 156,000 terminals lease at a cost of $1,650 a month for one and $1,295 each for two or more; that adds up to the tidy sum of more than $2.5 billion a year.

He launched his news division in 1990 to provide breaking financial stories, the kind that move markets, to his traders on their terminals. Later, he added 24-hour radio and TV operations; neither makes a profit, but Bloomberg uses them to boost the company's name recognition.

Bloomberg professes to be a bit embarrassed that people perceive him as an egomaniac for putting his name on the machines and the news operation. "You want a name you can remember," he says, explaining that the terminals were first called Market Master, but when that trademark proved invalid, he switched to the name his customers already unofficially used. "Bloomberg is a name you can remember."

On election night in New York this past fall, Elaine's was so crowded that it was almost impossible to move without crashing into someone famous (Sorry, Uma Thurman! Whoops, my fault, Charlie Rose. Barry Diller and Diane Von Furstenberg, can I squeeze by?), and even Bloomberg, a co-host of the party, looked overwhelmed. Harvey Weinstein, another co-host, was genial, albeit succinct, when asked about Bloomberg, pronouncing, "He's a good guy. Write something nice."

Among reporters and politicians, Bloomberg's name has recently become synonymous with fabulous A-list parties. He dazzled the Washington elites last year with a post-prom after-party that followed the White House Correspondents' Dinner. There were mounds of caviar, a table laden with fresh sushi, and an army of security to keep out unwanted crashers. An invitation to this year's party is as coveted as a George W. nickname; even last Wednesday's episode of The West Wing had a joke about whether President Bartlet could get into the "Bloomberg party."

Last summer, hedging his political bets, Bloomberg not only gave a gala at the Republican convention in Philadelphia honoring George Pataki (Colin Powell stopped by) but also threw a Los Angeles bash for the Democratic convention's New York delegation. A semi-nude model, her breasts artfully covered with shells, perched over Spago's raw-seafood bar; movie stars mingled with Tom Brokaw, Charlie Rangel, Chuck Schumer, and ink-stained wretches from most of the New York newspapers. Mark Green, working the room, went over to thank his host and rival, then wandered by where I was sitting with other journalists. "I just told Mike, 'If you don't win,' " Green quipped, " 'will you at least cater my inauguration?' "