In what is rapidly becoming one of cycling's most remarkable stories, Lance Armstrong is leading the Tour de France, the world's premier bicycle race, just before the halfway mark.

The French newspapers call him "the extraterrestrial," but he is an American. He also is a cancer survivor and the man who almost single-handedly has revived a sport tarnished by widespread doping in last year's Tour -- though not without drawing some questions himself among the prickly French media.

Armstrong is the first American racing for an American team, U.S. Postal Service, to have a realistic chance of winning the Tour, which completed its 10th day today. When Greg LeMond won in 1986, 1989 and 1990, he raced for European teams.

Armstrong finished fifth in today's stage high in the French Alps, but maintained an overall lead of 7 minutes 42 seconds over his next rival, Spaniard Abraham Olano of ONCE-Deutsche Bank. To give an idea of how wide that lead is, the second- to seventh-place riders are separated by 2:36.

Today's stage from Sestriere in Italy to Le Grand Bornand in France was won by Italian Guiseppe Guerini. Guerini crossed the finish line despite a bizarre collision beforehand with a spectator, who not only thought he could stand in the middle of the road and take a photo but also then failed to move out of the way.

"Today the objective was to conserve the jersey," the yellow shirt worn by the leading rider, Armstrong said after the finish. "The others were very strong today."

None of them, of course, had been undergoing chemotherapy less than three years ago. At the time, Armstrong -- a 27-year-old from Austin -- was on the road to becoming a leading rider. He won the 1993 world championships and had just signed a contract with the French team Cofidis when he had testicular cancer diagnosed in October 1996. It also had spread to his abdomen, lungs and brain.

Four courses of vicious chemotherapy, plus surgery, saved him, but Cofidis dropped him. He was out for the 1997 season, though he watched the Tour from the sidelines. Armstrong's 1998 season began slowly, but after some time off to think, he won the Tour de Luxembourg and was fourth in the Vuelta de Espana.

He finished first on the opening day of this Tour, the time trials, and has dominated the headlines since. His designation as an extraterrestrial -- some papers call him a Martian -- is double-edged. It could be taken as a reference to his power and speed. Or, as Gerard Holtz of France 2 Television explained in a telephone interview: "Everyone is asking the question: How can he do that? Is it something about the treatment for cancer?"

In other words, is he taking some sort of performance-enhancing substance? The question is not out of place in the world of professional cycling, particularly in the milieu of the Tour. A year ago, the race nearly came to a halt over allegations of drug use by riders.

Police searches allegedly found prohibited substances in the hotels of several teams; a Belgian masseur for the Festina team was arrested with his car's trunk stuffed with various performance-enhancing cocktails. Judicial proceedings are underway against 12 people in France as a result, including several riders.

Organizers banned five riders or officials and an entire team from this year's Tour in hopes of restoring the sport's image. One of the riders, Richard Virenque, a man whose Festina teammates and masseur said used banned substances, won his way back into the race in a court proceeding.

So doping is on everyone's mind. After today's stage, Holtz asked Armstrong on French television about the "questions."

"It's not true," Armstrong responded in halting French. "Incredible."

It was a strange scene. Sitting next to Armstrong on the TV stage, and helping to translate, was none other than LeMond, who praised Armstrong's performance and determination. Across the table was legendary Belgian champion Eddy Merckx, who said: "I tip my hat to him. I find all these suspicions in the newspapers really terrible."

And two seats away, listening with great interest and saying nothing, was Virenque.

Holtz said in the telephone interview that Armstrong has breathed life and hope into European cycling, at a time when it was needed.

"Before the time trials, everyone was thinking about the scandals," he said. "There was a lot of tension. Armstrong added a new tone, as if great music was pulled from cacophony. The whole mood changed."

Armstrong's supporters, American and otherwise, line the roads and call his name as he goes by. They wave American flags, and carry signs. On Tuesday, one read: "Armstrong: the renaissance of cycling."

CAPTION: As a fan waves Old Glory, American Lance Armstrong leads the pack during the 10th stage of the Tour de France. He finished fifth, but leads overall.