Goals from Roy Pook and Owen Hill earned Withdean a 2-0 win over Southall at Woodside Road.
With leaders AFC Wallingford losing 1-0 to Raynes Park Vale, their first defeat of the season, Withdean have renewed hope of winning the league.
Pook opened the scoring on 20 minutes with a smart finish which was helped into the net by a defender.
Hill sealed victory in the second half with a simple finish after a great run by Pook.
Goalkeeper Ross Standen kept a fourth successive clean sheet since joining from Lewes.
Withdean lie in sixth still 23 points adrift of the leaders but with eight games in hand.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article