The Labor Party has suffered a big fall in support in state elections in Tasmania and South Australia, with voters sending an ominous message to Kevin Rudd, who has to call a federal election before the end of this year.

Mike Rann appears to have scraped back into power in South Australia, winning a third term despite a swing of nearly 8 per cent against Labor, but in Tasmania it looks as if Will Hodgman's Liberals will form a minority government following a swing of 12 per cent.

If the weekend's swings were replicated federally, Rudd would be defeated.

However, commentators say Labor is more vulnerable at state level because of being in power for so long - 12 years in Tasmania, eight in South Australia.

The Rudd Government was elected only in November 2007. Local issues also figure more prominently in state elections.

Anthony Albanese, a government frontbencher, told ABC radio the results were better than forecast by the Liberals and their federal leader, Tony Abbott.

"They were predicting we'd be announcing two new Liberal governments in majority form in both states," he said. "It's clear that hasn't happened."

However, Abbott hailed the results yesterday as "very bad news for Labor everywhere, including Mr Rudd" and "very encouraging for Liberals everywhere".

He said: "It suggests to me that the Australian public are getting heartily sick of governments which are more spin than substance. This is Mr Rudd's problem."

Labor took comfort from the fact that it retained key marginals in South Australia.

Rann, who went into the election with a 10-seat majority, has been dogged by allegations of an affair with a former parliamentary barmaid, Michelle Chantelois, which he denies.

He appears set to retain 25 seats in the 47-member House of Assembly, with the Liberals holding 18 and Independents 4.

The results were bittersweet. He would be the third Labor man to win three SA elections. But in Rann's own seat of Ramsay, the swing against Labor was nearly 12 per cent and was even higher in core Labor seats.

In Tasmania, final results may not be known for days or even weeks, but the most likely outcome appears to be Labor and Liberals winning 10 seats apiece, and the Greens 5.

The Labor leader, David Bartlett, has already ruled out a deal with the Greens, and said before the election that the party with the most seats - or, in the event of a tie, the most votes - should have the chance to govern.

If that translates into a Hodgman minority government, Rudd will find it harder to push through health reforms that involve the Commonwealth taking control of ailing state-run hospitals.

Rudd said yesterday that he was prepared to work with any state premier, Labor or Liberal.

"I said on Friday that these two state elections would go down to the wire," he said. "[And] these two state elections have gone down to the wire."

Nationally, Labour is still more than 7 per cent ahead of the Liberals, on a two-party preferred basis, according to opinion polls.

Finance Minister Lindsay Tanner said: "I don't think there's much in the way of federal implications but obviously we always learn lessons from every election."