KEY POINTS:
Never mind who wins, Tour de France organisers just want cycling's blue riband event to emerge scandal-free from the three-week race which starts from London on Sunday.
The Tour desperately needs a smooth ride after a traumatic experience last year when Floyd Landis tested positive for elevated levels
of testosterone after winning the race.
American Landis has denied any wrongdoing and his case should be settled by a United States panel of judges and the French Anti-Doping Agency in the next few weeks.
"My wish for this Tour is to be sure the rider who will raise his arms on the Champs-Elysees is the real winner of the race," Tour director Christian Prudhomme said.
The war against doping has taken its toll this season again with 1996 winner Bjarne Riis admitting to cheating and 2006 Giro d'Italia champion Ivan Basso saying he had intended to take banned substances.
Kazakh Alexander Vinokourov is the favourite in the absence of the suspended Basso, the retired Jan Ullrich and Giro d'Italia winner Danilo di Luca and fellow Italian Damiano Cunego, who have both opted to skip the Tour.
Astana leader Vinokourov has a score to settle at the Tour. His team were barred from starting last year's race after five of their nine riders were implicated in a blood-doping scandal.
Vinokourov, who finished third overall in 2003 and fifth in 2005 after winning in Briancon and on the Champs-Elysees, has a strong team behind him.
German Andreas Kloeden, who left T-Mobile for Astana and ended third overall last year, Kazakh Andrej Kashechkin and former Giro champion Paolo Savoldelli are expected to pull the experienced Vinokourov in the mountains.
Vinokourov bounced back from the disappointment of missing last year's Tour by producing a career-best ride to win the Vuelta d'Espana.
He started 2007 focusing only on the Tour de France.
"I have already won what I wanted to win in the sport, with the exception of the Tour, and that is my big dream," he has said this year.
"So it is not really too risky in that respect. I will therefore prepare in the best possible way for the race."
Vinokourov said he would not be Astana's sole leader, despite his good relationship with the sponsors.
"Andreas [Kloeden] showed before that he can do very well in the Tour. There will be two leaders and the team will play it tactically to ensure we do as well as possible. The main objective for Astana is to win the Tour de France," he said.
Kloeden, who was one of Ullrich's lieutenants alongside Vinokourov in his T-Mobile days, finished second overall in 2004 behind seven-times winner Lance Armstrong.
Astana will have to make do without Matthias Kessler after the German rider was suspended by the team following a positive test for testosterone last April.
Italian Eddy Mazzoleni, third in this year's Giro, has been left out because of his implication in a doping probe.
Vinokourov's armada will need to hold off the challenge of CSC, who have two potential winners in Luxembourg's Frank Schleck and Spaniard Carlos Sastre
The Caisse d'Epargne challenge will be led by Spaniards Alejandro Valverde and last year's surprise runner-up Oscar Pereiro, backed by Russian Vladimir Karpets.
Australian Cadel Evans, who ended fifth overall last year, is gunning for at least a podium finish, as is Rabobank's Denis Menchov, sixth in 2006.
