Cadel Evans' vision of repeating as Tour de France champion vanished under the sun-baked punishment of the Pyrenees mountains on Wednesday, as Bradley Wiggins took another step toward taking the yellow jersey home.

French fan favorite Thomas Voeckler took a starring role into big climbs along the Spanish border, winning Stage 16 in a breakaway as Wiggins kept his big rivals a bay -- or dusted them.

"It's pretty much the Tour de France over for me," Evans said.

The 35-year-old Australian fell from fourth to seventh overall, and trails Wiggins by 8 minutes, 6 seconds, after struggling on the last two of four climbs in the stage. He cited stomach problems.

"When you have it two hours before the race there's not a lot you can do," Evans said. "I did not think it would affect me in the race, but obviously that's not my normal level."

As if the four ascents weren't hard enough, cycling's big event was also trying to get over the re-emergence of another longtime challenge: The doping-marred image that has hung over the sport.

Late Tuesday, Frank Schleck of the RadioShack team was sent packing after cycling's governing body UCI said an anti-doping lab's test on his urine turned up a banned diuretic. The 32-year-old Luxembourg rider placed third at last year's Tour.

Two big final shakedowns in the race await in Thursday's stage in the Pyrenees, featuring an uphill finish, and Saturday's time trial, though other pratfalls and pitfalls could await.

But Wednesday's stage went a long way toward shaping up the likeliest Tour podium when the race ends Sunday in Paris: Wiggins, Sky teammate Christopher Froome, and Vincenzo Nibali of Italy. They all gained key breathing space by beating their 10 closest chasers by about 1, 2 or 5 minutes.

"There was a pretty big selection made," said Tejay Van Garderen, an American who at sixth eclipsed Evans as top-ranked BMC rider. "It was obvious that Nibali, 'Wiggo' and Froome were a notch above my group. ... Sky is looking incredible, Nibali is making the race at least exciting."

Voeckler dominated the 123-mile course from Pau to Bagneres-de-Luchon, the Frenchman leading a breakaway for his second stage victory of the Tour. He also won Stage 10 and has four in total.

"Every one of the mountain passes was a race for me," said Voeckler, who captured the polka dot jersey for the best climber from Fredrik Kessiakoff of Sweden. "Today I did what many young riders dream of doing -- leading everyone over all four summits.

"I knew every kilometer of this course today, and it served me well."

Chris Anker Sørensen of Denmark was second, 1:40 back. Wiggins, Froome and Nibali finished together, 7:09 back of Voeckler.

Overall, Wiggins leads Froome by 2:05 and Nibali by 2:23. Jurgen Van Den Broeck of Belgium moved up to fourth, 5:46 back -- though he lost nearly a minute to Wiggins. Evans was nearly 4 more minutes back.

A bunch of 38 riders broke away early, but the climbs took their toll and the group divided. Cyclists first scaled the Aubisque and Tourmalet passes -- two of the toughest climbs in cycling -- followed by the category-1 Aspin and Peyresourde passes. The last peak was nearly 10 miles from the finish, before a long descent.

Voeckler grimaced, his jersey unzipped and his body rocking from side to side in rhythm with his pedal strokes as he climbed the ascents.

"I'm the first person to admit that I'm not beautiful on the bike," the Europcar rider said. "I'm a frowner. ... That's my way of doing it -- when I'm in pain, that's the way (I) look."

On the ascent to the Aspin pass, the day's third big climb, Evans started to lag. The Australian couldn't keep pace with BMC teammate Amael Moinard of Belgium.

Evans was about 40 seconds back of his teammates but recovered and joined the pack by the foot of the day's last climb after receiving an escort. But Evans struggled on the last climb, continuing to lose time afterward.

BMC pulled out the stops to help its leader, but it wasn't enough.

"A couple of times we tried to give him gels and some food and he was just saying something like his stomach was not handling it that well," said Van Garderen. "So maybe the heat was getting to him."

Evans crossed the finish line by clasping hands with U.S. veteran George Hincapie.

"The year's not over but certainly the retirement present I wanted to give to George Hincapie this year, the hope and wish for that is gone," said Evans.

On the Peyresourde, Nibali took his chances. His first attack against Wiggins gained some traction, and he held a 10-second lead for nearly a mile. But Froome, playing the dutiful lieutenant for Wiggins, led his team leader back. Nearing the top, when the pass got its steepest, Nibali struck again -- but this time, Wiggins did the hard work to catch him quickly.

Dave Brailsford, the Team Sky manager, said his two star riders never appeared to be under pressure -- and spoke in superlatives about Wiggins and his quest to become the first Briton to win the Tour.

"The last 18 months he's put together is nothing short of remarkable," said Brailsford. "I dont know any other -- certainly British athlete -- that has performed at his level for the same period of time."

Two American veterans ran into mishaps. Chris Horner, riding in his sixth Tour, had just fixed a punctured tire when he veered into some bushes, requiring a new bike to return to the race.

On the downhill from the Tourmalet pass, 17-Tour veteran Hincapie crashed and required treatment for his injured left shoulder and knee from team staff and the race doctor.

Thursday's 17th stage offers the last big day of mountain climbing, with an 89.7-mile slog up three hard ascents that includes an uphill finish from Bagneres-de-Luchon to Peyragudes.