Napoli went 12 points above second-placed AC Milan at the top of Serie A after beating Salernitana 0-2 on Saturday night.
Giovanni di Lorenzo scored shortly before half-time, and Victor Osimhen added another after the break for the visitors.
Nigeria International, Osimhen is now three goals above Inter’s Lautaro Martinez in the race for Serie A Golden Boot.
Napoli are looking to end their 33-year wait for a Scudetto, having not won it since Diego Maradona was their captain.
Luciano Spalletti’s side have lost only one league match this season, a 1-0 defeat by Inter Milan earlier this month.
They have won the Serie A title twice before, in 1986-87 and 1989-90.
Napoli’s advantage could be narrowed to nine points should AC Milan beat Lazio, who are fourth, on Tuesday.
Third-place Inter, meanwhile, take on Empoli on Monday.