Dover suffered their first home league defeat of the season after losing 2-1 against Eastleigh at Crabble on Tuesday.
James Constable's double secured the win for the Hampshire side and some sweet revenge following Whites 5-2 win against them in September.
Ricky Modeste was on target for Dover, who despite the loss, remain third ahead of Saturday's trip to second-placed Forest Green Rovers. Whites will start that game three points behind the home side.
Dover started strongly and almost took the lead in the opening minute when Ricky Miller's lob beat former Dover goalkeeper Ross Flitney and dropped just over.
Flitney was called into action 12 minutes later after pushing away Aswad Thomas' dangerous cross with Jack Parkinson hovering behind him.
Not long after, the same three players produced an action replay, only this time Flitney caught the ball.
Miller went close to opening the scoring in the 22nd minute when his snap shot from Modeste's lay-off hit the side-netting.
Dover continued to press and Sean Raggett saw his header from a Nicky Deverdics corner scrambled away.
It was Eastleigh who then had two decent chances in quick succession with Will Evans and Jai Reason both firing just wide.
Eastleigh were enjoying a bit of pressure and it needed a stunning save from Andy Rafferty to prevent them opening the scoring.
Josh Payne's 25-yard free-kick looked destined for the top-corner before Rafferty, making his first league start of the season in place of the suspended Mitch Walker, turned it away for a corner.
Rafferty was beaten three minutes before half-time when Paul Reid's header from a corner crashed into the underside of the bar and was cleared.
Eastleigh started in the same fashion after the break with Constable shooting wide just seconds after play resumed.
Dover responded with Stefan Payne having his effort from outside the box saved by Flitney.
But it was Constable who did finally make the breakthrough in the 51st minute when his shot from inside the box deflected off Raggett to beat Rafferty.
Modeste put Dover back on level terms 12 minutes later after punshing a mix-up in the centre of the Eastleigh defence to fire past Flitney.
But the joy was short-lived with Eastleigh regaining the lead two minutes later from the penalty spot.
And Rafferty almost prevented it happening.
Sam Magri fouled Reason, captain Ben Strevens took the kick and Rafferty dived low to his right to keep it out.
Strevens followed up but Rafferty saved his effort before the ball fell to Constable to finish off.
Dover went in search of a equaliser and Modeste had an effort cleared off the line, Parkinson headed over before Modeste hooked another effort wide.
Eastleigh substitute Ross Lafayette had a shot well saved by Rafferty before Flitney's legs denied Payne.
But there was to be no saving Dover losing for a second consecutive match at Crabble following Saturday's FA Cup exit at the hands of Stourbridge.
Dover: Rafferty, Magri, Orlu, Grimes, Raggett, Thomas, Parkinson, Deverdics, Modeste, Miller, Payne. Subs not used: Murphy, Diallo, Ofori-Acheampong, Sterling, Ajala. Attendance: 913