Although there are no former winners of the Tour de France racing this year, there are a handful of Grand Tour winners. Gilberto Simoni and Damiano Cunego could ride the Tour if they wanted to (though being Italian
I doubt either of them will they're opting out). And of course, the last two Vuelta winners are Denis Menchov and Alexandre Vinokourov. So there are a handful of riders around who presumably know how to win over three weeks.
You wouldn't know it from the popular sentiment concerning Vino. While he has his believers, a decent portion of Cycling fandom believe he'll eventually blow himself up on a mountain stage... assuming the doping cops don't get him first. If this is true, then the Tour is completely wide open. And if it isn't, then Vino has to be considered a strong favorite. So... can Vino keep it together over three weeks, every day?
The case against him is based largely on his most recent Tour in 2005, when he had a jour sans on the first day in the Alps, stage 10 to Courchevel. The next day he rebounded for a stage win on a long solo break, lost more time in dribs and drabs, then wrapped up the Tour by finishing third in the final ITT to Lance Armstrong and Jan Ullrich. Vinokourov's only other Tour worth considering (and that itself is debatable) was in 2003: then, he came second only to Iban Mayo on Alpe d'Huez, won the next day in a solo attack, and hung with or not far behind the big boys every day through the time trials and Pyrenees before dropping two minutes in the final ITT, at which point his podium place was firmly established. [Vino was injured in 2004.]
Actually, although 2003 was a long time ago, that race may actually be a better barometer for Vino. This was the year Jan Ullrich was off on his COAST-Bianchi hiatus, and the only time Vinokourov has gone to France with a solid team (T-Mobile) slated to work for him. By 2005, Ullrich and Andreas Kloden were both back in pink, so whatever Vino accomplished in that Tour was done without clear GC ambitions, or in spite of team in-fighting... take your pick. Anyway, but for one bad day, Vino's last two tours have shown him riding very consistently, just off the pace of the top climbers but ahead of all but the ITT specialists in the time trials.
For what it's worth, in last year's Vuelta Vinokourov was bad in the first mountain stage, losing two minutes to Alejandro Valverde and others, a time he recouped largely on an escape over some middlin climbs to Granada. Vino then cemented his lead on the next day's hills and in the final time trial, which he won outright (after running third in the prior ITT). Vino overcame a bad day's climbing early on; stayed with Valverde and co. on the other mountain stages, and eventually made his decisive move. Maybe that's further evidence he can blow himself up on occasion, amidst otherwise solid performances. But Vino's calendar was turned upside down by Operacion Puerto, and his appearance at the Vuelta was a last-minute grasp at revenge for a lost year, so all of this must be taken for the oddity it is.
So there is little reason to expect Vinokourov to have a jour sans somewhere along this year's Tour route. Unlike any grand tour he's entered since 2003, Vino comes in at the head of a solid team, and following a year-long training program intended to reach his peak at the Tour. Yes, he like anyone could have a bad day, but there's no reason to sit around waiting for it. Moreover, he's got a very consistent, excellent record in grand tour time trials, better than anyone still racing, and save for a few specialists who will benefit from this year's flat courses, Vino probably will not be bested by any of his main rivals. Really, I think he's going to win the Tour.
On the other hand, I'm actually not as blown away by his supporting cast as some observers may be. Paolo Savoldelli is one of my favorite guys out there, but he's a time trialist and downhiller more than anything else, two disciplines that don't offer much in support of others, and he tends to climb at his own careful pace. Andreas Kloden would be an outstanding teammate... if he decides to be. But Klodi and Vino are famously not that close, and Klodi could be forgiven (based on his two superior Tour results) for thinking he has the best shot this year among the Astanas. Andrey Kashechkin probably will help Vino a good deal; they work well together and Kash's bonk in the Dauphine should be written off as training. Matthias Kessler just got suspended, and Eddy Mazzoleni is hanging by a thread in this regard... assuming he's not already exhausted from the Giro. They're running dead-last in the karma department, and it could get worse. I'm not saying this is a bad team by any means, I'm just saying they're not as useful for the Tour as CSC and Caisse d'Epargne appear to me.