Lance Armstrong powered his way through the most punishing stage of the Tour de France yesterday and kept a firm grip on the yellow jersey, thanks to another reassuring effort by his Discovery Channel team. Escorting him from start to finish over three grueling climbs, the blue-and-grey train rolled into Briancon a safe 1 minute and 25 seconds behind Stage 11 winner Alexandre Vinokourov (T-Mobile) and Santiago Botero (Phonak), giving their champion an even better chance at swiping his seventh straight Tour victory.

“We are in a good position,” Johan Bruyneel, the team’s manager, said afterward. “It is up to us now to defend it.”

The closest competition is still Mickael Rasmussen (Rabobank), whose third straight command performance in the mountains firmly established him as a threat when the Tour arrives in the Pyrenees this weekend.

The biggest disappointment in the Tour so far has been the T-Mobile squad, which is loaded with contenders but so far has failed to put up much resistance. Veterans Jan Ullrich and Andreas Kloden are a distant ninth and tenth, respectively. But Vinokourov’s courageous performance after sputtering in the Alps on Tuesday may give T-Mobile some momentum. Indeed, the day’s headlines belonged to Vinokourov.

Despite torrid heat in the valley, the stoic Kazakh mounted his first attack early on the Col de Madeleine, a strenuous 6.1% grade. This early challenge did not phase team Discovery – but Vinokourov was accompanied up the Madeleine by a score of other riders, including Botero and his teammate, eighth-placed Francisco Mancebo.

Led by Manuel Beltran, the Discovery Channel riders turned up the pace and swallowed up a number of the escapees just before the summit, but Vinokourov sped ahead as Botero struggled to keep up. At one point it looked as if the Colombian would be engulfed by the peloton, but with a kilometer to climb, he cranked past Vinokourov and sailed over the Madeleine summit in front, with his teammate Oscar Pereiro in tow. They were soon joined by Basque rider Egoi Martinez (Euskaltel).

The four escapees built a two-minute lead as they cruised down the back side of the Madeleine and sprinted along the wide, flat highway that made its way up to the next mountain, the Col du Telegraphe. It is the shortest of the three climbs, but an integral part of this stage of attrition – a handful of lesser riders waved to their team cars, putting an end to their Tour.

On the zig-zagging incline, the Phonak teammates and Vinokourov dropped Martinez and went on to lead the peloton by about three minutes all the way to the third and final climb.

Team Discovery seemed content to let Vinokourov and Botero lead, but kept them on a tight leash. Down on their saddles despite the grueling grade, they took turns escorting Armstrong up the Tour’s highest peak, the fabled Col du Galibier. Riders succumbed to the relentless gravity and tumbled off the rear of the peloton; massive crowds on both sides of the narrow mountain road brushed up next to them, cheering, taunting, just inches away.

Armstrong was in solid company, though, escorted by his right-hand man, George Hincapie, and Giro d’Italia champion Paolo Salvoldelli, who thrives in the heat. Their captain spoke into his mouthpiece, discussing strategy with Bruyneel. Enough real estate remained between the Galibier summit and the finish in Briancon – about 25km – that they could eat into Vinokourov’s and Botero’s three-minute lead on the downhill.

Coasting over the summit, tucking newspapers into their shirts as protection against the cold wind, Armstrong and what remained of the peloton sank into aerodynamic crouches and began the risky descent. It was wet in patches, and the roadside dropped off into fatal precipices. Still, they closed in on Vinokourov and Botero, knocking more than a minute and a half off the lead by the time they reached the finish.

Botero seemed poised to steal the stage in the final 500 meters, and kept looking over his left shoulder to see when his opponent would make him move. Poker-faced, Vinokourov waited to the waning seconds and then sprinted. Botero was out of gas, and could only watch as the powder blue and yellow colors of the Kazakh national champion power across the paint.

A lot of riders will no longer be in the game after yesterday. Former yellow-jersey holder Jens Voigt was eliminated after he dragged himself into Briancon in 168th place, 46 minutes behind. On a sorrier note, Italian rider Dario Frigo was arrested by French police after illegal performance-enhancing drugs were found in a car his wife was driving.

Discovery Channel was wise to save at least a little energy on this stage and refrain from chasing down the lesser threats, and some riders may not have the strength to continue. The Alps are not done, and no smart rider will underestimate the 187km trek from Briancon to Dignes les Bains.