Bordeaux-Begles scored a try six minutes into added time to win 37-36 at Clermont on Saturday and continue their Top 14 revival.
A week after a late penalty gave them a one-point victory away to Racing, Bordeaux-Begles trailed by seven points with five minutes to play but fought back to jump from sixth to fourth in the table.
Two of their rivals for a top-six place lost tight matches later on Saturday.
Toulon, who started the weekend in third, finished with 14 men and went down 25-23 at Brive while Lyon lost 18-17 at home to Pau and stay seventh.
"It's hard to beat a team that never gives up," said Bordeaux-Begles coach Christophe Urios.
Clermont started the day one place above their visitors but cracked under late pressure.
"Our indiscipline costs us dearly. We had a good victory but showed bad game management in money time," said Clermont coach Franck Azema.
They conceded a 75th-minute penalty which Maxime Lucu converted.
In the 82nd minute, Nathanael Hulleu, a second-half substitute, crossed the line for the visitors, but the try was ruled out after review.
Clermont centre Jean-Pascal Barraque received a yellow card, though, for a deliberate knock-on in the build-up.
Bordeaux-Begles were rewarded when winger Hulleu touched down in the corner while Alivereti Raka tried to haul him out of play.
This time the try was given and Raka received a yellow card for a high tackle.
The home team also lost Japanese back Kotaro Matsushima, who limped off after 18 minutes with an apparent thigh injury.
Bordeaux were unbeaten in five games in January, all against teams in the top-seven places. The only match they did not win was at home to Clermont on January 16, when a late penalty by Barraque gave the visitors a 16-16 draw.
"After a diabolical series of matches, I am proud of the players. I saw a team of winners," said Urios.
Toulon fell short of a dramatic comeback in Brive. When visiting centre Duncan Paia'aua was sent off for a dangerous tackle after 54 minutes, Enzo Herve converted the penalty to put the home team 25-13 ahead.
Yet the 14 men fought back, as Beka Gigashvili scored a try and Sonatane Takulua kicked a conversion and a penalty, but missed another kick at goal with two minutes left.
"What bothered me was our lack of precision in the scoring areas. That's why the missed penalty at the end of the match is trivial," said Toulon coach Patrice Collazo.
"What bothers me is that we played better with 14 than with 15."
In Lyon, the home team scored the only two tries of the match and led 17-12 after 62 minutes. Pau landed all six of their penalty attempts, with Antoine Hastoy booting over the last one with eight minutes to play.
"It's a combat sport," said Lyon coach Pierre Mignoni. "To go all the way, you have to be hungry... Do the players want to be in the top six?"
The top-of-the table match at La Rochelle has been postponed after a cluster of coronavirus cases at leaders Toulouse.