The Nationals' Dave Layzell maintained his lead with 52.5 per cent of the two-party preferred vote on Monday, while Labor's Peree Watson had 47.5 per cent, with 48.2 per cent of the vote counted.

Both sides agreed the outcome would be determined by the results of the Singleton pre-poll booth that contains 6500 votes.

"It's really too close to call before we see what's in the pre-poll vote," Ms Watson said.

In addition, there were 5000 postal votes and 21,000 pre-poll votes cast.

Electoral commission staff spent the majority of Monday counting upper house votes. They expect to turn their attention to the pre-poll votes on Tuesday.

The Nationals are hoping they can hold the two per cent swing that appeared during Saturday night's vote.

However, as counting in other close seats on Monday showed, pre-poll votes can change things dramatically.

At the close of voting on Saturday, Mr Layzell told his supporters he was feeling positive about the party's prospects of retaining the seat.

"(The results) look positive at the moment; I'm certainly not upset about where we are," he said.

Earlier in the evening, he referred to "some pretty awful things", which had occurred during the campaign.

"In the last few weeks the campaign really intensified. We have seen a lot of personal attacks and I have found that very confronting," he said. "It's the first time I have had to deal with these sorts of personal attacks but, of course, that is politics. You've got to toughen up and take it knowing that I am the face of government in this seat."

Meanwhile, Labor's red tide continued to rise across the Hunter on Monday.

Clayton Barr in Cessnock, Jodie Harrison in Charlestown, Jenny Aitchison in Maitland, Tim Crakanthorp in Newcastle, Kate Washington in Port Stephens, Yasmin Catley in Swansea and Sonia Hornery in Wallsend all built on their sizeable leads during the day.

With 50 per cent of the vote counted in Wallsend, Labor's Sonia Hornery had secured almost 83 per cent of the vote.

With a 6.8 per cent swing, the party managed to increase its stranglehold on one of the state's safest seats.

It was a similar story in Newcastle, with Labor's Tim Crakanthorp securing 75 per cent of the vote after 63 per cent of the vote had been counted.

The party also built on its 2019 result with a swing of 7 per cent.

Elsewhere, Labor's Kate Washington had a massive 16.6 per cent swing towards her. Ms Washington had secured 72.3 per cent of the vote after 45 per cent had been counted on Monday afternoon.

Maitland's Jenny Aitchison had secured 68.8 per cent, a 4.1 per cent swing, with 79 per cent of votes counted.

In Cessnock, Clayton Barr had secured 73.5 per cent of the vote, an 8 per cent swing, with 42 per cent of the vote counted.

Yasmin Catley had 66 per cent of the vote in Swansea with 63 per cent of votes counted.

Lake Macquarie Independent MP Greg Piper had 71.8 per cent of the vote after 58 per cent of the electorate's vote had been counted.