Nick Xenophon has admitted he has not done enough campaigning in the seat of Hartley, with a new poll showing the two-party preferred vote is at 49 per cent to 51 in favour of his Liberal opponent Vincent Tarzia.

Mr Xenophon's concession came as the Liberals stepped up their fight against the SA Best leader in the seat in Adelaide's east, distributing mock instant scratchie tickets labelled the "Xenophon Lottery".

When players scratch the face of the former No Pokies MP, the faces of Labor MPs are revealed beneath, and there are references to government failures and bungles.

According to the latest Galaxy poll conducted for Newscorp, Hartley is shaping up as a two-horse race between Mr Xenophon and Mr Tarzia.

Mr Tarzia leads with 38 per cent of the primary vote, Mr Xenophon trails with 30 and Labor's Grace Portolesi lags behind at 22.

Mr Xenophon admitted that as leader of his party, he had not spent enough time in his own electorate.

"I feel a bit like Vegemite, I've been spread a bit thin but I'm doing my very best," Mr Xenophon said.

He said the number of houses he had doorknocked were in the hundreds, but he said that was "not enough — it should have been in the thousands".

Nick Xenophon says he's been "spread a bit thin" and hasn't spent enough time in Hartley. ( ABC News: Simon Royal )

Mr Xenophon is facing an additional challenge in his electorate, with Labor and Greens preferencing the sitting Liberal candidate ahead of him.

"My plea, my message to Labor and Greens voters is that if they vote for Labor or the Greens in the seat of Hartley, they'll be effectively delivering the seat to the Liberals and to Mr Marshall," Mr Xenophon said.

Mr Tarzia won the seat of Hartley from Labor at the last election, and it has been the target of extra Liberal resources since Mr Xenophon announced he would run there.

Defeated Xenophon would remain as adviser

Throughout the campaign, Labor has tried to portray Mr Xenophon as a Liberal, and the Liberal Party saying a vote for SA Best is a vote for Labor.

One voter in the area who received the mock lottery ticket contacted the ABC, describing it as a "nasty trick" that strengthened her intention to vote for Mr Xenophon.

Mr Xenophon said his party's elected MPs would elect their own parliamentary leader if he failed to win Hartley, but said he would remain in an advisory role.

"If Liberal, Labor, the Hotels Association, the pokies barons think they'll get rid of me so easily, I'll be around to fight for people and I'll be around to support my team because I think from the poll we've seen today we're a real chance in a number of seats," he said.

Mr Xenophon ruled out replacing any successful SA Best Legislative Council candidate in a casual vacancy.

But he would not be drawn on whether he would seek paid work in the office of one of his newly elected MPs, in the same way he did for former staffer-turned-senator, Rex Patrick.

"Ask me that after Saturday night because I'm intending to win the seat of Hartley," Mr Xenophon said.

Mr Xenophon might be at odds with the major parties on many issues, but he has called on both to get behind his latest election promise.

He wants $5 million for South Australians to be able to access clinical trials and cutting-edge immunology treatments for rare cancers.

"It means that people ... won't have to travel interstate every two weeks and go through that trauma and expense in terms of their treatment," Mr Xenophon said.

"It'll mean more South Australians can get access to cancer treatment and if nothing else comes out of this campaign and we get this off the ground, then I feel that this campaign would have been worth it."