Luton remain strong favourites for the League One title but could only claim a point at home to Gillingham.
The Hatters are five points clear of Barnsley - who drew with Doncaster on Friday night - after the Gills twice came from behind at Kenilworth Road with goals from Tom Eaves and Luke O'Neill cancelling out strikes by Danny Hylton and Jack Stacey.
Sunderland are still two points ahead of Pompey but had to come from behind to beat Walsall 2-1 at the Stadium of Light. A Liam Roberts own goal and a Will Grigg effort did the trick for them.
Behind Pompey, Charlton were held to a 0-0 draw at Bristol Rovers while Coventry won 2-1 at Peterborough thanks to goals by Amadou Bakayoko and Bright Enobakhare.
Blackpool's play-off hopes were hit in a 3-0 loss at Burton, but Fleetwood remain in the top ten after a 2-0 home win over Plymouth.
Shrewsbury - who host Pompey next Saturday - eased their relegation worries with a 2-1 home win over Wycombe and it was a real relegation six-pointer at the Kassam Stadium which Oxford won 1-0 with a late goal by Jamie Mackie. AFC Wimbledon triumphed 1-0 at Southend.