American rider Levi Leipheimer, a Discovery Channel teammate of Contador, won the 19th stage with a time of 1 hour, 2 minutes, 44 seconds in the 35-mile race against the clock from Cognac to Angouleme.

Contador lost most of his lead but still holds a 23-second advantage over Cadel Evans. Barring a crash or other mishap, the 24-year-old Spaniard is likely to bring home the yellow jersey Sunday in the 20th and final stage - a 90.7-mile ride from Marcoussis to Paris' Champs-Elysees that is usually a processional ride with few chances for breakaways.

"I'm eager to go home and celebrate," said Contador, who was encouraged during the time trial by seven-time champion Lance Armstrong, who has ties to Discovery and was riding behind in a team car. "It wasn't an easy day."

The latest doping allegations didn't help.

French daily Le Monde, citing what it claimed was an investigation file it had access to, said today that Contador's name, or initials, appeared in documents found at the apartment of Spanish doctor Eufemiano Fuentes, at the center of the Spanish doping probe known as Operation Puerto.

Contador said he was "sure" that he was not involved in the case, and insisted he was innocent. He said he would give a DNA sample to prove it if asked, but wouldn't offer one if it wasn't requested "because I'm innocent and I don't have to prove anything to anyone," he said.

Contador inherited the leader's yellow jersey after former Michael Rasmussen was ousted Wednesday by his Rabobank team, which said the Dane had lied about where he was when he missed a doping test last month.

Italy's Cristian Moreni and pre-race favorite Alexandre Vinokourov were also ejected after testing positive for doping.

Evans, meanwhile, conceded that he had missed his chance to win, attributing his defeat to having fallen back in the Peyresourde climb in the Pyrenees at the beginning of the third week.

"I was close to winning the Tour de France," he said.

Contador's Discovery Channel teammates are likely to go all out Sunday to protect his lead, and ensure that rivals don't overtake him on the ride up to the finish on the famed Paris avenue.

"We've won this Tour de France - barring a freak accident tomorrow," Leipheimer said of his team. "I am obviously very happy for Alberto."

A brief, discreet visit to Angouleme by Armstrong "motivated" the team, Leipheimer said.

If all holds, Contador will win with the second-closest margin of victory ever at the Tour. The record was American Greg Lemond's 8 second edge over France's Laurent Fignon in 1989.

"This Tour has been crazy, crazier than expected," Contador said.

Contador came into the stage with a 1 minute, 50 second lead over Evans - and Saturday's big question was whether he could hold off the Australian.

Leipheimer, who had come in 2:49 back of Contador in third place overall, now trails him by 31 seconds. It was his first stage win at the Tour.

"I didn't know in the warmup that I'd be so good," Leipheimer said. "It's a special day and today I had the best legs of my life."

Contador is riding in his second Tour, after winning this year's Paris-Nice race. He didn't take part in the race last year because his former Astana team was disqualified after five of its riders were implicated in the Spanish blood-doping probe.

He would be the Tour's youngest winner since Jan Ullrich in 1997.

"I think cycling is crazy now, we see that there are a lot of problems," Contador said. "It's clear that we can't continue with all the scandals and all the problems we had."