Lewes' promotion hopes could be shattered by their recent poor run which was extended to five games without a win as they went down 2-0 at home to a hardworking Croydon side.
The defeat leaves Lewes in second place but now just one point ahead of Bognor, who have a point advantage over Horsham.
Bognor will leapfrog the Rooks if they win tomorrow night's Sussex derby at the Dripping Pan.
Lewes started brightly but against the run of play the visitors took the lead on 22 minutes with a fortunate goal after a clearance from Lewes goalkeeper Russell Tanner struck the back of Croydon's Darren Hall and rebounded into the net.
Lewes's bad luck continued on 43 minutes when they had what seemed a perfectly good goal disallowed for offside after a melee in the area saw a Croydon defender turn the ball into his own net via a post.
Five minutes after the interval the Rooks should have drawn level when a good move ended in a cross from the left by Tony Reid which Paul Kennett turned into the path of Matt Allen who somehow drove his effort high and wide.
The crucial second goal came in the 57th minute when Hall was allowed too much freedom to carry the ball down the right flank and cut inside before beating Tanner with a fine low shot.
Seven minutes from time impressive Lewes substitute Lee Newman was put through but saw his goalbound strike well saved by Matt Martin.
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