Armstrong has two weeks remaining and a series of tortuous climbs through the mountains to prove he is worthy of a fourth consecutive championship in cycling's most famous event, but Spain's Igor Gonzalez Galdeano emerged Monday as a potentially dangerous rival.
The 52-kilometer ride against the clock from Lanester to Lorient separated the would-be challengers from the true threats and Armstrong covered the distance in one hour, two minutes, 29 seconds.
That was 11 seconds behind stage winner Santiago Botero of Colombia, who began the day in 30th place overall and moved all the way to fifth. It was the first time since 1999 that Armstrong had not won an individual time trial at the Tour de France.
Gonzalez Galdeano started the day in first place, 34 seconds in front of Armstrong, and held onto the yellow jersey that goes to the overall leader by finishing fourth in the time trial --- 19 seconds behind the winner and eight seconds behind Armstrong.
Armstrong moved from eighth place overall into the No. 2 position --- 26 seconds behind Gonzalez Galdeano, who finished fifth in last year's tour.
The 182 riders remaining from the original field of 189 will have Tuesday off before taking part in a relatively easy ride that will carry them into the foothills of the Pyrenees. On Thursday, the mountain tests will begin and that is where Gonzalez Galdeano must show he has the endurance to hold off Armstrong.
After Botero and Armstrong in the individual time trial came Serhiy Honchar of the Ukraine, who was 18 seconds off the pace. Gonzalez Galdeano was next, followed by Laszlo Bodrogi of Hungary (25 seconds back), Raimondas Rumsas of Lithuania (25 seconds), David Miller of Britain (50 seconds) and Dario Frigo of Italy (1:34).
Gonzalez Galdeano and Armstrong distanced themselves from the rest of the field with their time trial performances.
Joseba Beloki of Spain was in third place overall, 1:23 behind. He was followed by Honchar (1:35), Botero (1:55) and Andrea Peron of Italy (2:08).
The biggest casualty in the time trial was Franch star Laurent Jalabert, who suffered a puncutre and fell from 12th to 18th in the overall standings, 4:18 behind the leader.