Argentine Lucho was involved in all four goals as Marseille, who have a game in hand, moved on to 62 points from 31 matches and boosted their hopes of landing their first league title since 1992.
"There's always something you can complain about but I have to say it was a really good performance from us tonight," Marseille coach Didier Deschamps told French television channel Canal Plus.
"We were strong physically and combined well with some really nice moves."
Ivory Coast forward Bakari Kone latched on to a through ball from Lucho to open the scoring from close range late in the first half.
Lucho then sent in a cross for defender Stephane M'Bia to head home early in the second period.
The Argentine also set up the third for Mathieu Valbuena and it was from his 74th-minute corner that Souleymane Diawara headed the fourth.
Nice pulled one back through midfielder Emerse Fae deep in added time.
AUXERRE SECOND
A late goal by Daniel Niculae gave Auxerre a 1-0 win at Nancy which put them in second place.
The Romanian forward struck from close range two minutes from time to put his team on 60 points from 32 games.
Olympique Lyon are third, four points off the lead, after a 1-1 home draw with Lille.
Forward Pierre-Alain Frau put Lille ahead with a deflected shot on 62 minutes but the home side levelled nine minutes later with a header from Brazilian defender Cris.
Lille's Portuguese defender Ricardo Costa and Lyon midfielder Maxime Gonalons were sent off in the second half.
Girondins Bordeaux's title dreams were dented by a 3-1 defeat at Paris Saint-Germain on Saturday.
The champions are fifth, six points off the pace, but have a game in hand on the leaders.
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