Citroen's Sebastien Loeb won five of Saturday's six stages of the Rally of France to extend his lead over the Finn Mikko Hirvonen to 52.4 seconds.
The French driver, who also snatched Friday's six opening stages, could seal his fifth consecutive world title this weekend in Corsica.
Hirvonen's teammate Francois Duval is a further 4.3 seconds behind in third.
Jari Matti Latvala in another Ford is in fourth, ahead of Subaru's Petter Solberg.
There are four more stages on Sunday before the finish.
Loeb, who has 96 points from 12 rallies, leads Ford's Hirvonen by 12 points in the world championship standings with two races remaining, in Japan and Britain.