It is axiomatic for athletes in big-time sports to take their challenges one day at a time. So it was a surprise when Paul Cayard, front-runner in the America's Cup challenger semifinals and the United States's best hope to bring the Cup home from Down Under, veered unbidden into an impassioned speech Sunday about what he'll do if he wins this event, the so-called Mount Everest of yachting.

It's too early to think that way--way too early--but that's Cayard. He is sailing's most impressive one-man band: CEO, skipper, fund-raiser and fearless leader of AmericaOne, the No. 1 challenger here. Able to deliver interviews on demand in French, Italian or English, Cayard is dark, mustachioed and handsome and desperately seeking to replace Dennis Conner as the world's most famous sailor.

The only way to do that, said Cayard when he won the 1998 Yachtsman of the Year Award after an unexpected triumph in his first Whitbread 'Round the World Race, is to bring the America's Cup home again, the way Conner did from Australia in 1987.

Cayard is well on the way, the favorite to advance to two-boat challenger finals Jan. 25 after winning six of seven races so far in the 10-race semifinals. If he can then make it through the best-of-nine challenger finals, it's just a matter of beating Team New Zealand in the Cup match in February--no small matter.

But things are looking up for Cayard. He entered these semifinals worried sick that bad luck could deep-six his exhaustive, two-year, two-boat, $30 million quest. Queer weather, untimely gear breakdowns and plain old bad breaks could gang up on anyone, he reckoned, in a series that pitted six boats against each other for 10 straight days.

AmericaOne has had only one unpleasant surprise so far, a broken headstay fitting on the second day of racing that led to its only loss, and sits alone atop the standings more than halfway through the series.

Cayard looks relieved. But he's not the sort of fellow who rests halfway through a climb, nor stops looking up. As he sat in AmericaOne's spacious, spotlessly clean compound Sunday, watching his crew ready the boat for a race against Le Defi Francais, he launched off on his own ambitious plan to improve the Cup if he brings it home.

"I want independent, professional management" to replace the antiquated, yacht club-based system in place for 150 years, he said, adding that he would try to run the event like baseball or football, with a regular schedule and professionals to negotiate TV rights and regulate the venues.

Cayard ridiculed the current system, in which he said competitors spend too much time hammering out and then interpreting ever-changing rules that often wind up favoring the host country in its efforts to keep the Cup.

"We just need one guy with the guts to do it," Cayard said. "The first guy who stands up and says, 'I might lose, but I'll set this thing up so it will last 50 or 100 years,' all the others will follow."

Cayard said he has a signed agreement with Saint Francis Yacht Club, whom he represents here, to pursue his aims if he wins. "I made a speech," he said, "and told them the most honorable and memorable thing they could do after winning it is to fix it. They bought into it and now they're very proud of it."

Cayard went on to describe the format he would put in place in San Francisco Bay: a shorter regatta of six to eight weeks, shorter races and more of them, shorter breaks between rounds, less wasted time. He grew animated. "But I can't do anything until I win," he said. "I've pushed everybody else but nobody has the guts."

It's vintage Cayard--one man alone against the world.

His record suggests he has never tilted at windmills, tackling hopeless goals like Don Quixote. Cayard sailed in the last two Cup matches, in 1992 for Italy and in 1995 as helmsman for Conner's Stars & Stripes, and dominated the field in his first attempt at the Whitbread two years ago. His current run for the Cup has jelled remarkably in the last month as crew work, boat speed and tactics all seemed to peak at the right time.

Being fund-raiser, chief executive, skipper and coach of a multimillion dollar athletic quest is a bit like asking Washington Redskins quarterback Brad Johnson to do his job plus Daniel M. Snyder's, Norv Turner's and Vinny Cerrato's. How has he handled it?

"Don't forget husband and father," said Cayard with a weary smile. "That's pressure."

AmericaOne has weathered hard times that appear to be largely behind Cayard. A year ago, when he still lacked the corporate sponsors needed to ensure he could build a second boat--the key to successful speed development--he said he spent many sleepless nights wondering how to pay for work already in progress and still keep the train running toward a distant goal.

"There was a lot going on," said the San Franciscan, 40, now in his fifth Cup campaign. "I've been buried in fund-raising, working the phones. But now I'm fully in the boat. I hadn't spent a lot of time with the crew, learning the boat, working on sail shapes. All these subtleties require a lot of personal attention from me.

"The way we're doing this may not be the best way but things are what they are and the hard part is over. Our money is okay. I'm focusing on sailing."

And looking, as ever, ahead. Far, far ahead.