Scott Murfin grabbed an 89th-minute winner as Chichester sunk Hassocks 3-2 to climb back to the top of the table.
Paul Thomas and Tony Stephens put the hosts 2-1 ahead after James Laing fired the Robins in front but Ian Dawson then restored parity. Murfin clinched the three points which could prove crucial.
Boss Adie Girdler said: "There is everything to play for now. We have got ourselves back in to it and we are back on track.
"We have some big games coming up with Redhill, Three Bridges and East Preston to play at home."
East Grinstead warmed up for the RUR Cup final against Three Bridges tomorrow with a 2-0 win at struggling Pagham.
After a goalless first half Nick Levitt, making his debut at full back, gave Grinstead the lead in the 62nd minute before the home side were denied a clear penalty when Lee Stevens was taken out in the area. Steve Banks wrapped things up with 15 minutes to go.
Grinstead boss Bobby Smith said: "We have not been playing particularly well in the last couple of weeks so I made a couple of changes to freshen things up and it worked. It is a good omen for the final."
Bridges also won 2-0 on the road, Pat Massaro's double earning them victory at Selsey.
A Michael Morgan hat-trick helped Redhill to a 4-2 victory over Sidley, who were reduced to ten men in the first half when Jimmy Watson was dismissed for violent conduct.
Morgan opened the scoring with a cross which caught on the swirling wind and the visitors went 3-0 up as Bronek Dearowa and Morgan struck again. Sidley hit back through Adam Day and Ben White but Morgan completed his treble to seal the points for the visitors.
Ringmer and Whitehawk fought out a 1-1 draw. Stuart Garrod followed up Dominic Shepherd's diving header to score for the hosts after Matt Hill had put Hawks in front.
Rye and Iden United came out on top in a seven-goal thriller at home to Sidlesham and stay fourth.
Goals from Michael O'Callaghan, Ade Olorunda, Duncan McArthur and Peter Baker cancelled out a brace from Richie Davies and a Dave Towers strike.
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