Stalemate over the next federal member for Wannon could drag out for at least a week

Incumbent MP and frontrunner Dan Tehan has indicated he will not make any statement until either the Australian Electoral Commission declares a winner, or his opponent concedes the race.

Mr Tehan is well ahead on first preference votes with 38,087, after roughly 80 per cent of ballots have been counted.

Independent candidate Alex Dyson sits in second place with 17,122, around 900 votes ahead of Labor's Gilbert Wilson.

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Mr Dyson is banking on significant preference flows from the other candidates to boost his vote, saying he thought it would be foolish to concede when there was still a mathematical chance he could win.

"We will just have to wait for the votes to be counted," he said.

In Australia's preferential voting system, ballot counters start by tallying first preference votes for the candidates. If none of the candidates have more than 50 per cent of the votes from first preferences, the candidate with the fewest votes is knocked out and each of their ballots is reallocated to whoever was listed as the next preference on the ballot paper.

This is called the distribution of preferences.

As a shortcut in this "two candidate preferred", or TCP, process, the AEC predicts who the top two candidates will be, so that when candidates start getting knocked out the vote counters can immediately allocate those ballots to one of the two favourites and produce a head-to-head winner.

In Wannon the AEC assumed Mr Tehan and Mr Wilson would be the top two vote getters, but on Saturday night Mr Dyson was ahead of Mr Wilson and the AEC had to ditch its TCP count, meaning the overall winner wasn't clear cut.

On Monday afternoon an AEC spokesman said it still wasn't clear who out of Mr Dyson and Mr Wilson would end up with the second most first preference votes, so they still couldn't start distributing preferences.

He said for the moment they would have to keep counting the first preference votes as they trickled in.

He said all of the election day votes had been counted, along with almost all the pre-poll votes but there were still thousands of postal votes and absentee ballots - where people registered to vote in Wannon have cast their ballot outside the electorate - still coming in.

While Mr Dyson is sitting 876 votes ahead of Mr Wilson, postal votes have been favouring Mr Wilson two to one, and with more than 10,000 postal votes still to be counted it remains possible Mr Wilson could jump into second place.

The AEC spokesman said because the gap between Mr Wilson and Mr Dyson would probably narrow further, the distribution of preferences would probably be done once all the votes had arrived, which could take another week or two.

The final TCP result will be much closer if Mr Dyson ends up facing off against Mr Tehan, because Labor and The Greens both recommended putting Mr Dyson ahead of the Liberal incumbent, whereas Mr Dyson didn't give preference recommendations on his how-to-vote card.

The current TCP estimate for Mr Tehan against Mr Dyson is roughly 55 to 45 per cent, whereas for Mr Tehan and Mr Wilson it is more like 60 to 40.

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