Weekend opinion polls indicated that Prime Minister Malcolm Fraser, the tall conservative farmer who has dominated Australian politics for the past eight years, is facing defeat Saturday in an early election called by him.

If the polls are right, Fraser faces an almost impossible task in seeking to stave off a challenge from the Labor Party, led for less than a month by charismatic former union leader Bob Hawke.

One poll, conducted by the national newspaper The Australian, indicated Hawke was in the lead, 52 to 39 percent, with the remainder split among undecided voters and minor parties. Others show Fraser trailing by 10 percentage points.

Last Saturday, Fraser scrapped the strategy of vigorous attacks on Hawke and Labor's policies, which had served him badly during the first three weeks of the campaign, and decided to spend the last week campaigning as a statesmanlike, experienced prime minister better qualified than his opponent to steer through difficult economic conditions.

Fraser is making a series of short addresses to the nation in an attempt to persuade the 9.5 million voters that his plan for a mild expansion of government spending and a wage freeze for 12 months will lower inflation and unemployment rates--both over 10 percent--and set the country to take full advantage of a world recovery.

Labor has proposed a much larger injection of government money into the economy, with job programs, a new national health plan, increased social welfare programs and a radical policy on prices and incomes, spelled out in a 37-page agreement between Hawke and the Council of Trade Unions.

Fraser described that policy as a "socialist manifesto" which would give unions a veto over decisions of a Hawke government and give unparalleled power to communist-led unions.

Based on the social contract that British Labor governments a decade ago drew up, the document pledges his government to implement policies quite radical for Australia. They include price controls and extension of the current wage freeze--imposed in December for six months on wage earners--to the incomes of corporations, small businesses and professionals.

Unions would have a say in annual reviews of the tax scales and income taxes would be cut immediately by 5 percent for low- and middle-income workers. Higher brackets would face a 5 percent increase. Immigration would be cut back.

Fraser made what is generally regarded as a monumental political blunder early in the campaign by declaring that Labor intended to finance its program by using funds that Australians traditionally keep in banks. He said that if Labor won, "your savings will be safer under the bed than in the bank."

Hawke described Fraser's outburst as the most irresponsible act ever committed by an Australian prime minister. Several leading bankers, traditional supporters of Fraser and his conservative Liberal Party, said he could trigger a run on the banks. Fraser explained that he was merely using "graphic" words to highlight the lack of detail in Labor's plan on financing the deficits it would trigger.

Fraser has a deserved reputation for coming from behind late in elections and his tactics could still win this one, especially as the TV addresses examine more closely the details of Hawke's policies. There has been little public examination or debate so far in the campaign.

But Fraser has given the appearance of panicking in the face of defeat. The press unanimously condemned what were called his scare tactics.

Fraser's electoral victory in 1975 was the biggest landslide in Australian history. Two years later, he repeated the performance and drove former prime minister Gough Whitlam out of politics.

A former policeman, Bill Hayden, became leader of the Labor Party, and made the 1980 election a close race. But Fraser won, by most accounts because in the last few days he suggested that Labor planned to introduce a capital gains tax.

Hawke entered Parliament in the 1980 election and immediately signaled his intention to challenge Hayden for the leadership. He narrowly lost a formal challenge last July. But four weeks ago, almost at the hour that Fraser was calling the election, Hayden resigned under pressure from within the party.

Hawke became leader unopposed. An electric orator, he has criss-crossed the country stressing to huge, emotional rallies that Australians can "trust me." His slogan, unprecedented in the rough-and-tumble politics here, is: "Bringing Australia together."

Fraser's argument, endorsed by many commentators, is that Hawke's populist policies would trigger new inflation and unemployment and drive away foreign investment. But the signs are that the public is not listening to Fraser's arguments.