Buying and racing thoroughbreds is so risky an investment, so expensive a hobby, that it may seem hard to comprehend why a rational person would spend millions of dollars this way. But anyone who observes Bob Lewis, the owner of Charismatic, will immediately understand the sport's irresistible appeal.

It is rare to see an adult exude such excitement and joy as the 75-year-old Californian does when his horses are involved in big races. And never has a horse owner expressed his elation better than Lewis did after Silver Charm's 1997 Kentucky Derby victory. Asked at the post-race news conference whether this was his biggest thrill in racing, he replied that it was one of the biggest thrills of his life, and declared: "I want this on my tombstone: `Loving husband, adoring father and winner of the 123rd Kentucky Derby.' " Lewis seems more ebullient than ever as he awaits Saturday's Belmont Stakes, which might require the chiseling of another line: "Owner of the 12th Triple Crown winner, Charismatic."

Although racing has been one of his lifelong passions, Lewis waited most of his life before he allowed himself to indulge. He got his first exposure to the sport when his parents took him to Santa Anita in 1934. He and his future wife, Beverly, went to the races at Portland Meadows while they were attending the University of Oregon. They honeymooned at Del Mar. They live in the shadow of Santa Anita. Yet Lewis didn't start buying thoroughbreds until 1990. "I've always felt that if you get into something, you do it right," Lewis said. "That's why I didn't get into racing before our economic circumstances permitted it."

Lewis worked long and hard to achieve those circumstances. When he left college, he supported himself by driving a beer truck; he became a salesman, and then a sales manager, for a California brewery. Concluding that his best chance for success was running his own distributorship, he made a successful pitch to Anheuser-Busch Cos. and launched his business on a shoestring. "Beverly kept the books," he recalled. "My partner and I each drove a truck. We had one employee. We were poor as church mice -- and that's no kidding. We rejoiced that we were able to eke out a small profit."

When the business started growing, propelled by Budweiser's rising popularity, the Lewises had to keep reinvesting their profits. Their efforts paid off. Today the Foothill Beverage Company is one of the largest such businesses in California, selling 10 million cases of beer per year. Lewis finally felt comfortable about taking a multimillion- dollar plunge into horse ownership -- doing it, of course, in as businesslike a fashion as possible.

"I've employed the philosophy in business that you've got to have good chemistry with your management people; they make your success," Lewis said. "In racing, if there was any one factor that was important it would be the selection of our trainers." In 1990 Lewis met an up-and-coming trainer, Bob Baffert, and told him, "We'd like to get on board with you," and bought his first horses. Later Lewis met Wayne Lukas and got more deeply involved. It wasn't a bad job of picking management people: Lewis had hired the two men who would be the decade's two most successful trainers in the Triple Crown series. And the rest is history.

The Lewises reached the big time in 1995 when their filly, Serena's Song, was the nation's champion 3-year-old filly, and Timber Country (in whom they owned a one-third interest) captured the Preakness. Silver Charm won the first two legs of the Triple Crown in 1997 before narrowly missing a sweep in the Belmont Stakes. Charismatic has duplicated Silver Charm's achievement, and he is about to give the Lewises an unprecedented second shot at racing's greatest prize.

Lewis has relished it all. He has become actively involved in national racing organizations and has promoted the sport tirelessly. After Charismatic won the Preakness, he addressed hundreds of media members and said: "As I've told all of you guys -- and gals -- you can call me any time, day or night. I'm always happy to talk to you." He is unfailingly diplomatic. When he won his first Derby with Baffert as the trainer, he went out of his way to praise Lukas.

When he won with Lukas this spring, he extolled Baffert. He is so relentlessly upbeat that some journalists consider him a little too saccharine, and so they were surprised when Lewis recently displayed a trace of ire.

While Charismatic was winning the classics, the filly Silverbulletday was trouncing members of her sex, and Baffert, who trains her, was publicly pondering whether to enter her in the Belmont. He thought the filly might be the best 3-year-old of either sex in America, but said he didn't want to rain on Lewis's parade -- i.e., spoil his own client's bid for the Triple Crown. Lewis responded with what was as close to a public rebuke as he will ever deliver. He proposed that he and Baffert bet $100,000 against each other on Charismatic vs. Silverbulletday.

A couple of days later, Lewis was his usual diplomatic self, saying that he "humorously took affront" at Baffert's remarks; that "Bev and I are so appreciative" of all that Baffert has done for them; and that he welcomes Silverbulletday's entry in the race to give Charismatic a definitive test. But the incident revealed that there is a little more steel in Bob Lewis than some people in racing had suspected. This is, after all, a man who made tens of millions of dollars in a business he built from scratch, and doing so requires more than a smile and a cheerful sentiment.

But if Lewis does harbor any resentment about the idea of Baffert trying to derail his Triple Crown bid, he will never give another hint of it. Lewis will be gracious if Charismatic loses Saturday, gracious and irrepressibly exuberant if he wins.