At Priestfield on Tuesday, the Gills took an interval lead over the Shrimpers through Danny Kedwell's penalty and though Bradley Dack was sent off for violent conduct in first-half stoppage time, they preserved their clean sheet and top spot.
Free-scoring Vale remain second after a thumping away win over Fleetwood, who drop from third to fourth.
Vale went ahead just before the half-hour mark at Highbury through the in-form Tom Pope and Ashley Vincent quickly doubled their lead with his third goal in as many games.
Junior Brown pulled a goal back before half-time but Pope's second restored the two-goal margin and Louis Dodds struck twice to make it 5-1.
Steven Gillespie scored a consolation goal from a penalty but Fleetwood were overtaken by Exeter, who twice came from behind to beat Wycombe.
Gareth Ainsworth struck after four minutes for Wanderers but Exeter hit back through Arron Davies (29).
Dean Morgan's looping header restored Wycombe's lead but was immediately cancelled out by Jamie Cureton before Danny Coles put the Grecians in front for the first time and they held on to win 3-2 at St James Park.
Bradford's 3-1 home win over Morecambe took them fifth ahead of Accrington, who were beaten 4-3 in a thrilling game at Chesterfield.
Kyel Reid set up James Hanson's opener for Bradford (45) at Valley Parade and then scored the second himself (80). Jack Redshaw pulled one back but Gary Jones killed the game off three minutes from time.
Jack Lester and Marc Richards put Chesterfield 2-0 up inside 11 minutes at the Proact Stadium but Romuald Boco pulled one back (28) and Peter Murphy equalised (58).
Lester made it 3-2 to the Spireites but Boco also netted his second as Stanley levelled once more, though they then lost Michael Liddle to a straight red card for a professional foul - and it proved crucial as Terrell Forbes headed Chesterfield's winner from a corner.
Rochdale ended Rotherham's unbeaten home record since moving to the New York Stadium with a helter-skelter 3-2 win.
Veteran Dele Adebola put Dale ahead on the stroke of half-time but Alex Revell equalised on the hour and five minutes later, Daniel Nardiello put the hosts 2-1 up.
Bobby Grant's penalty levelled the game (75) and Kevin McIntyre put the visitors ahead for the second time in the game with 11 minutes remaining.
Cheltenham inflicted a fourth defeat in a row on Oxford, Darren Carter and Shaun Harrad putting the hosts 2-0 up before Peter Leven pulled one back from the spot with 10 minutes remaining.
Rene Howe gave Torquay a 1-0 win at AFC Wimbledon and Aldershot's Craig Reid scored the only goal against Barnet.
Northampton were also 1-0 winners thanks to Adebayo Akinfenwa's goal away to Dagenham & Redbridge while Plymouth Argyle and Bristol Rovers drew 1-1.
Conor Hourihane put Argyle ahead (35) at Home Park but with 70 minutes on the clock, Rovers equalised through Tom Parkes.
