Wiggins is currently 00:02:05 ahead of the second-place rider, Christopher Froome. If he is unable to maintain that lead and cross the finish line by the time the peloton crosses the finish line at Paris Champs-Elysees, it will be one of the most terrible collapses in recent memory.
It's not as though Wiggins has a rival on his tail. Froome is his teammate, and he is specifically riding alongside Wiggins to ensure that his team leader becomes the first rider from Great Britain to win the Tour de France (via The Guardian).
Italian Vincenzo Nibali is the only other man within three minutes of Wiggins, and perhaps the only one who stands a puncher's chance at overtaking the 32-year-old leader.
Cadel Evans sits 00:03:19 back of Wiggins. He seems to be sputtering a bit, but it's impossible to count a defending champion out, despite how gloomy things look for his quest to repeat.
Wiggins is not only at a huge advantage for the remainder of the Tour because of the gap between him and his rivals. Saturday's Stage 19, from Bonneval to Chartres, is a time trial. If there's one area where Wiggins can separate himself from the rest of the field even further, it's in the penultimate stage.
He won the first time trial of the Tour—a 29-mile ride in Stage 9—by 35 seconds over Froome, and nearly a minute over third-place finisher Fabian Cancellara.
Stage 19 is 33 miles from start-to-finish. If Wiggins is able to hold off Cancellara—who will be one of his biggest competitors in the stage—he should have no problem in basically locking up the win a day early.
Current Garmin-Sharp manager Jonathan Vaughters, who Wiggins once rode with, offered his interpretation of Wiggins' chances in the race's final stretch (via SI.com):
"Brad's biggest rival in this race is Brad, in his own head, and as long as he stays calm and focused then he's going to win it. I've always felt that this Tour was going to be a runaway for Wiggins."
There are two brutal stages ahead that will force riders to navigate the uphill terrain of the Pyrenees, but if Wiggins can keep his nearest competitors from overtaking him on Wednesday and Thursday, there's no reason he shouldn't win the 2012 Tour de France easily.