The Coalition may have swept into power on an anti-government swing of more than 4 per cent in the lower house, but was extremely unlikely to gain a Senate majority.

The Coalition has 16 sitting senators from the 2010 election, so must secure 23 of the 40 seats being contested in this election for an upper house majority. Pre-election simulations had suggested the most likely result for the Coalition was 16 seats again, for a total of 32 in the Senate, seven short of a majority.

The swing to the Coalition in early counting appeared too weak to change that prediction, with the Palmer United Party claiming much of a stronger swing against Labor.

However, the strength of the swing to the Coalition in Tasmania increases the government's chances of snaring a third Senate seat in that state, to Labor's two, with the Greens facing a surprisingly strong challenge from the Palmer insurgency for the state's sixth Senate spot.

The PUP was showing up even more strongly in early counting of Senate votes in Queensland, where the new party had doubled the Greens' vote, albeit with a count of less than 4 per cent.

Across the nation, only about a dozen Senate seats are in play, with half of these likely to be determined by a labyrinthine flow of preferences among a record number of minor party candidates.

On pre-election polling figures, simulations had shown the Greens could win six Senate seats, taking their total to 12, but the early counting was not encouraging for the party.

The next most likely result is an assortment of minor party candidates on the right of politics holding the balance of power.

The major parties usually split the first four of the six seats in each state by winning primary votes equal to or close to two quotas, or 28.6 per cent, and early counting pointed to a repeat.

If their candidates fall below a quota in the territories, the door opens for the Greens at the Coalition's expense in the ACT and an ex-Labor independent who could oust the ALP in the North Territory. Both major parties were hovering in the danger zone in the territories' early counting.

In its strongest states, NSW and Western Australia, the Coalition is eyeing a primary vote closer to three quotas, 42.9 per cent, than two. Three hours into the vote count, the new government was around the mark and was also above three quotas in Queensland.

A strong showing by the PUP was again making the Greens nervous in the north.

In most states, Labor hopes not to drop into the danger zone well below the two-quota mark — the danger is greatest in the West.

In South Australia, Nick Xenophon was expected to win a quota in his own right, while Greens Senator Sarah Hanson-Young hoped her primary vote holds above 9 per cent, or else the sixth seat becomes a minor party raffle, with the No Carbon Tax Party a potential beneficiary.

A small shift in the vote can make all the difference by putting one party ahead of another and altering the direction of preference flows down the chain.

This makes predicting the overall make-up of the Senate hazardous, but early vote counting pointed to a PUP Senate presence, which would make life interesting for the new Abbott government.