Przemyslaw Frankowski scored a second-half penalty as Lens beat lowly Auxerre 1-0 on Saturday to reduce Paris Saint-Germain's lead in Ligue 1 to three points.
The Poland international converted from the spot with an hour gone as Lens made it 10 wins from as many home matches in the league this season.
"Knowing how to win these types of matches, even if it's difficult, is very important," said Lens coach Franck Haise.
"We like to win with style but I'm not going to get angry because we didn't have the match of the century."
Lens have 44 points, their highest total at the halfway stage of any top-flight season. The club won their only Ligue 1 title in 1997-98.
"I don't know what the second part will be like, but the first half of the season has been outstanding," added Haise.
Auxerre slid to a fifth straight defeat and had defender Isaak Toure sent off shortly after the goal. They sit two points from safety in 19th and second to last place.
Marseille are two points adrift of Lens in third after coming from behind to defeat Lorient 3-1 at the Velodrome.
Terem Moffi's 12th goal this term put Lorient ahead but Sead Kolasinac headed Marseille level before halftime.
Alexis Sanchez drilled the hosts in front early in the second half and Jordan Veretout added a third as Marseille reeled off a sixth successive victory in the league.
Laurent Blanc's Lyon slipped further off the pace in the fight for the European places with a 2-1 home defeat by struggling Strasbourg.
Goals from Jean-Eudes Aholou and Habib Diallo in the space of three first-half minutes put the visitors in control and they held on despite Alexandre Lacazette's penalty.
Strasbourg moved out of the relegation zone and have taken four points in two games, after a draw with Lens in midweek, since sacking coach Julien Stephan on Monday.
PSG's trip to Rennes on Sunday is set to be the first time their superstar front three of Lionel Messi, Kylian Mbappe and Neymar have all played together since the World Cup.
Rennes have won their last eight home league games but lost top scorer Martin Terrier for the rest of the campaign to a knee injury two weeks ago.