South Australian Liberal Lucy Gichuhi has been relegated to an unwinnable spot on the party's Senate ticket, all but confirming her exit from parliament at the next election.

The senator joined the Liberals in February after entering parliament as an independent to replace disqualified Family First senator Bob Day last year.

But she wasn't able to convince SA party members to put her in a winnable spot on the upper house ticket, with Adelaide councillor Alex Antic grabbing third place.

Senior Turnbull government minister and SA senator Simon Birmingham said Senator Gichuhi had put in a solid effort in trying to convince party members to support her.

Picha: AAP/Mick Tsikas

"This may not be the last we'll ever see or hear of Lucy," Senator Birmingham told 5AA radio on Monday.

"We've got an election campaign to go through and we hope that we can win as many spots as possible."

Senator Gichuhi failed in her bid to snare third spot on the ticket despite public support from Malcolm Turnbull and former prime minister John Howard.

READ MORE Liberal senator Lucy Gichuhi bills taxpayers $12,000 for five Sydney trips

Assistant Agriculture and Water Minister Anne Ruston leads the SA Liberal ticket, with senator David Fawcett picked at number two.

Last month, Senator Gichuhi blamed an "administrative error" for the misuse of thousands of dollars in entitlements.

Senator Gichuhi, 55, billed taxpayers more than $2000 to fly two family members to Adelaide in October last year for her 50th birthday.

SBS News has contacted Senator Gichuhi's office for comment.