The Australian Electoral Commission will distribute preferences that morning and declare the winner in the afternoon.

By late Wednesday, the counting of below-the-line votes had Labor's Kate Lundy on 34.19 per cent of the primary votes, Mr Seselja on 33.24 and the Greens' Simon Sheikh on 19.44 per cent.

The nominal quota for an ACT Senate seat is 33.33 per cent of the vote, and will be calculated when all votes are counted.

The commission has been inputting votes from tens of thousands of below-the-line votes for the past two weeks. Two surprising results of the ballot were the fall in Labor's support and the approximately 30,000 votes cast for minor parties.

Senator Lundy has retained her position, while the winner of the second seat will be sworn in when Parliament sits.

Territory senators serve the same term as the House of Representatives, while state-based senators serve a fixed term, with the newly elected members not entering the Senate until next July.

Mr Seselja was speaking more confidently of victory in the ACT Senate race, after being welcomed into the first meeting of Coalition MPs. The ceremony for the declaration of the poll will take place in the historic Kings Hall at Old Parliament House.

The draw for places on the ballot was in the former Senate chamber and the building was used as a polling station for the first time during this election, proving popular with voters.

The Animal Justice Party, which has first place on the ACT Senate ballot paper, is directing its preferences to the Liberal Party.

It put the Greens last in retaliation against ACT Greens MLA Shane Rattenbury, the Minister for Territory and Municipal Services, who authorised the cull of about 1450 kangaroos to protect rare grasslands. The Rise Up Australia Party is directing its preferences to the Liberals. The Stable Population Party has three tickets, two with preferences for the Greens, one for the Liberals.

The other minor parties directing preferences to the Greens over the Liberal Party are Katter's Australian Party, Bullet Train for Australia, Drug Law Reform, Sex Party, Voluntary Euthanasia Party, Palmer United Party and Australian Independents.

An informal distribution indicates that if the Liberal Party receives all the preferences from Rise Up and Animal Justice and one third of the preferences from Stable Population Party, Mr Seselja would win another 4276 votes, bringing his support to 79,842.

If Mr Sheikh receives all the preferences from minor parties favouring the Greens, he would receive an extra 25,092 votes, bringing his support to 69,287 votes. Senator Lundy currently has 77,736 primary votes.

In the 2010 election, she received 92,271 first-preference votes. Liberal senator Gary Humphries received 75,576 and Greens candidate Lin Hatfield Dodds received 50,600.

■ The Palmer United Party has won its first seat at the election, with its candidate Jacqui Lambie taking out the final Senate seat in Tasmania.