Senator Trood, who was elected from the normally unwinnable fourth place on the Coalition's Queensland Senate ticket in 2004, risks becoming the first casualty of a likely surge in support for the Greens.

But after Labor agreed to direct preferences to the Greens in the Senate, in exchange for the minor party's support in crucial lower house marginals, the LNP began sounding out supporters in the fringes.

The Australian Electoral Commission requires groups' voting tickets for the Senate to be declared today.

Liberal deputy Senate leader George Brandis is first on the LNP ticket, followed by Nationals Senate leader Barnaby Joyce, with Liberal Brett Mason third, the rankings finalised during the 2008 merger of the state parties into the LNP.

Senator Trood said yesterday his only hope of joining his colleagues next term was Labor losing primary vote support, and the LNP rallying other Senate candidates to help him see off the threat posed by the Greens.

"It's not impossible," Senator Trood said. "It's not over yet. I remain optimistic."

An LNP source said a decision on preferences would not be made until this morning.

The Greens expect their lead Senate candidate in Queensland, Larissa Waters, to be elected and the party to hold the balance of power in the upper house.

Labor's ticket is topped by Special Minister of State Joe Ludwig and veteran senator Jan McLucas, with unionist David Smith in the vulnerable third spot.

SEAN PARNELL