Peni Ravai sent Bordeaux-Begles to the Top 14 summit as his late try secured a 20-15 victory over La Rochelle on Sunday.
A club-record crowd of 38,503 saw the match at Matmut Atlantique hang in the balance at 15-15 going into the final 10 minutes.
However, Fijian prop Ravai was driven over in the 72nd minute as Bordeaux pushed for the victory that at one stage had looked a formality.
They led 12-0 after half an hour behind four penalties from Matthieu Jalibert, only for Jules Plisson to hit back with four successful kicks of his own to tie the match.
Jalibert nudged Bordeaux ahead again in the 55th minute but Plisson soon replied again, setting up the close finish from which Ravai emerged as the hero.
Bordeaux head coach Christophe Urios, quoted on the team's Twitter page, said: "We can say it was a perfect afternoon, even if we complicated the task.
"I'm going to have a very, very good Christmas. Now what is important is [the December 29 match against] Pau."
Bordeaux nudged ahead of Lyon, who were beaten on Saturday at Castres and fall to second place.
Pau had debutant Ben Smith sent off as they suffered a 21-18 defeat away to Stade Francais.
The All Blacks great was dismissed after 50 minutes for leading with his elbow when challenging opposition hooker Lucas Da Silva, landing a blow around the neck area.
In the late game, Toulon nudged up to third place after winning 41-19 at home against Clermont Auvergne.