Coalition MP Ewen Jones is seven votes ahead of his Labor rival as counting continues in the final seat of Herbert.
A victory for Mr Jones in the north Queensland seat would give Prime Minister Malcolm Turnbull 77 seats in the 150-seat parliament.
This would enable him to retain an absolute majority and appoint a Liberal speaker.
A Liberal National Party scrutineer told AAP Mr Jones was seven votes ahead on Friday afternoon.
About 100 postal votes were being counted and a number of provisional votes were being processed ahead of their counting, which could go into Saturday.
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The electoral commission has to wait until 6pm on Friday for the final receipt of declaration votes.
The earliest-received postal votes were favouring Mr Jones, but the later ones were flowing in Labor candidate Cathy O'Toole's favour, likely due to the opposition's focus on Medicare in the final weeks of the campaign.
The LNP scrutineer said the final result would come down to about "20 votes either way".
The LNP has sought a recount of about 19,000 votes from two major pre-poll booths, Kirwan and Townsville City, where anomalies have been discovered.
But it is understood the recount has been rejected by local Australian Electoral Commission officials.
