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

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 at 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 and 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.

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: Its doping-marred image.

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 Sorensen 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.

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 look.’’

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In another Tour development, Luxembourg rider Frank Schleck, who was pulled from the race Tuesday after a positive test for a forbidden diuretic, denied taking any banned substance and suggested instead he may have been poisoned. The RadioShack Nissan Trek team leader said he ‘‘formally rejects’’ having taken any banned substance and requested the B sample to be tested.

‘‘If this analysis confirms the first result, a complaint will be filed against an unspecified person for poisoning,’’ the rider said in a statement.