The result at Crawley is hanging on a knife edge when officials were sent home after two counts failed to confirm a winner.
The count will be continued today at noon after it was decided the counters should start again afresh.
Tensions ran high as the first count drew to a close and candidates watched nervously from the gallery and the floor.
Sitting Labour MP Laura Moffatt arrived well after 3am in Labour red trousers and Conservative Henry Smith waited anxiously as tempers and temperatures rose as the count reached a late conclusion at 3.45am.
Hope gave way to more tension as a recount was announced with only 80 votes in between Labour and Conservative.
Ms Moffatt said: "To be honest I was expecting a recount.
"We've had some really hard issues to deal with and it's been tough."
Mr Smith said: "We realised today going around the constituency that it was going to be close."
Ms Moffatt added: "I hate counts. They make me so nervous."
Mrs Moffatt won at the last General Election with a majority of 6,770 votes and a turnout of 55.4 per cent.
A third count was ruled out after election officials decided the judgment of the counters could be called into question because they were all getting too tired.
A result was expected to be announced by this afternoon.
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