Both failed.
Lille equalised against Marseille in the 87th minute, extending their unbeaten run across all competitions to 16 matches, and Monaco were frustrated in a goalless draw at Reims.
Marseille remained second in the standings, ahead of Monaco only on goal difference. The Mediterranean rivals are four points behind PSG, who face in-form Lyon on Sunday.
Marseille were in the driving seat at Stade Velodrome until Bafodé Diakité levelled for 1-1.
Marseille led after 17 minutes after a well-constructed team move. Following a quick one-two, Luis Henrique passed to Adrien Rabiot down the right. The France international rushed toward the goal and served a low cross for Quentin Merlin, who dummied a defender by feinting a shot then fired in with his left foot.
Diakité's header came from Rémy Cabella's free kick.
Lille's string of nine wins and seven draws is the second longest unbeaten run in the club's history, according to Opta statistics.
"We played a great game and stuck to our plan: Stopping them from building through short passes in the center and then using the flanks and exploiting depth. I think we did that pretty well," Lille coach Bruno Genesio said. "It would've been harsh to leave without a point considering how we played. The game plan was followed perfectly."
Marseille finished with 10 men after Pol Lirola received a straight red card for a dangerous tackle on André Gomes in added time.
Lille were fourth, three points behind Marseille.
In the wake of their 3-0 loss at Arsenal midweek in the Champions League, Monaco struggled at Reims and came close to conceding in the 51st when Oumar Diakité's powerful right-foot shot crashed off Philipp Köhn's crossbar.
Monaco's best chance came in the 77th when Takumi Minamino had a one-on-one against goalkeeper Yehvann Diouf, only to miss the target. The Japanese midfielder had another effort in added time that flew over the crossbar.
Hampered by injuries, Monaco have been slowing down and showing signs of fatigue in recent weeks, winning just one of their past five matches in all competitions.
Also, Lens drew at Auxerre 2-2.
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