Bayern is on 57 points, ahead on goal difference from Dortmund, which won 3-1 against struggler VfB Stuttgart.
Thomas Mueller, Mats Hummels, and Jerome Boateng all started for Bayern, days after being dropped by Germany coach Joachim Loew.
Lewandowski added a second in the latter stages on his 150th Bundesliga appearance for Bayern to continue his prolific form against Wolfsburg, taking his tally to 16 in eight games.
Koen Casteels saved from Lewandowski and Gnabry, who opened the scoring in the 34th minute as he stabbed in Muller's low cross. It might yet go right down to the wire but with Bayern now leading the table, few would bet against the champions winning what would be their seventh title in a row.
"Stuttgart defended really well and were organised".
But Stuttgart levelled with Marc-Oliver Kempf in the 71st before Spaniard Alcacer notched his 14th goal of the season.
"They parked a very big bus", Dortmund coach Lucien Favre complained.
But all the momentum is with Bayern after its 12th win from 13 league games, while Dortmund - which had a nine-point lead - has only two wins from its last six.
Third-placed RB Leipzig were held to a goalless draw at home by Augsburg, who beat Dortmund last Friday and went down fighting against Bayern last month.
Hertha Berlin lost to Freiburg as Vedad Ibisevic's own goal sealed the 2-1 defeat in front of home crowd.