There have been some memorable finishes at L’Alpe d’Huez. But perhaps none of the 23 road stages that have finished atop the 21-turn mountain road has had as big an impact as that promised on Tuesday. With at least six riders still holding a serious chance of winning the 2006 Tour de France with six days of racing remaining, the hundreds of thousands of fans lining the 13.8km climb to the finish of stage 15 should witness a spectacular battle.

Before the two Pyrenean stages last week, then race leader Floyd Landis (Phonak-iShares) was given the biggest chance of winning this Tour. For many, he is still the top favorite, even though he gave up the yellow jersey to Oscar Pereiro (Caisse d’Épargne-Illes Balears) in a tactical move on stage 12 to Montélimar.

Assuming that Pereiro will cede his jersey on Tuesday’s 187km stage 15 — which features the hors-catégorie Izoard climb at 86km and Cat. 2 Lautaret at 134km before reaching the foot of the Alpe at 173km —Landis looks set to recapture the overall lead.

Going into the stage, these are the relative positions of the American and his principal rivals for victory in Paris:

Floyd Landis (USA), Phonak, 64:06:33
Denis Menchov (Rus), Rabobank, at 1:01
Cadel Evans (Aus), Davitamon, at 1:17
Carlos Sastre (Sp), Team CSC, at 1:52
Andreas Klöden (G), T-Mobile, at 2:29
Michael Rogers (Aus), T-Mobile, at 3:22
Levi Leipheimer (USA), Gerolsteiner, at 5:37

Let’s look at these six challengers individually:

Menchov: The winner of last year’s Vuelta a España (after the disqualification of Roberto Heras for doping) is a former winner of the Tour’s Best Young Rider award. The Russian has twice won Dauphiné Libéré stages on the Mont Ventoux summit and last week took the stage 11 win at Pla-de-Beret in a three-way sprint ahead of Evans and Leipheimer. He has the reputation for being an opportunist climber rather than one who takes the initiative.

Evans: The former Australian mountain-bike star’s climbing skills are well documented. He has won mountaintop stage finishes at the Tour of Germany, Tour of Austria and Tour of Tasmania. He was one of the strongest in last Thursday’s finish at Pla-de-Beret, where he finished fourth, 17 seconds behind the lead trio; but he would have preferred a steeper grade than the Spanish mountain’s 5.5-percent average. The Alpe tilts up at 7.9 percent with several pitches exceeding 11 percent. Evans hasn’t raced on the Alpe before now.

Sastre: The little Spanish rider won on the Ax-3 Domaines summit in the Pyrenees at the 2003 Tour, and climbed with Lance Armstrong to finish second behind breakaway Michael Boogerd at La Plagne in the 2003 Tour. His fifth-place finish, alongside Evans, at Pla-de-Beret should give him the confidence to attack on L’Alpe d’Huez.

Klöden: The German is not a dominant climber, but he did win stages on (lower) summit finishes at Paris-Nice and the Tour of the Basque Country back in 2000. He will hope for a steady pace on the Alpe. He’ll probably be unlucky in that respect.

Rogers: The lean Australian has greatly improved his climbing, which has never been bad. He performed well on mountain stages at the 2003 Route du Sud and Tour of Germany to win those races overall. That same year (and the last time there was a road stage up the Alpe), Rogers paced his yellow-jersey teammate Richard Virenque up to L’Alpe d’Huez on the Aussie’s Tour debut. He could surprise a few people on Tuesday.

Leipheimer: Riders who know him well say that the American’s climbing ability, particularly his resistance and acceleration, has improved dramatically in the past two seasons. That was shown at last August’s Tour of Germany when he won the stage to the summit of the highest and steepest summit finish in Europe above Sölden, Austria, where he defeated both Jan Ullrich and Cadel Evans. This year, Leipheimer was by far the strongest climber in winning the Dauphiné — especially on the Ventoux, where Menchov followed his wheel all the way up before sprinting for the stage win. Expect him to play an aggressive role on Tuesday.

And Landis? Given his current strong form and experience for pacing Armstrong up climbs similar to the Alpe, he will be a hard man to dislodge; and he knows that he has a potential win at Saturday’s time trial to keep his time buffer over his challengers.