IT'S a naive voter who believes everything that the politicians say at election time. But among the Australian electorate it's those who believed almost nothing who are being proven most accurate. In little more than four months since his Labor government's unexpected March 13 election win, Prime Minister Paul Keating has dumped or severely modified major election promises. And predictions are that this month's Federal Budget will see more pledgesrelegated to the backburner. The major polls differ on whether his government is ahead, though both show the gap between it and the Opposition as small. The latest Newspoll, released earlier this week, puts the government at 43 per cent, compared with 45 per cent for the Liberal-National Coalition - a drop in the Coalition's support and a showing as much to do with the disarray of its leadership as with the government's performance. Opposition Leader Dr John Hewson's key opponents continue their campaign to undermine him, with his former deputy, Peter Reith, restating his leadership ambitions this week. Dissatisfaction with Mr Keating's performance remains at 60 per cent but the sectors of the community who would seem to have grounds for dissatisfaction appear to be increasing daily. The two issues dominating the headlines here are the so-called Mabo legislation - the government's effort to get uniform national legislation to deal with a High Court judgment recognising Aborigines' native land title - and tax cuts. MABO - named after Eddie Mabo, the Aboriginal man who took the precedent-setting case to the High Court - has been a weeping sore since Mr Keating failed to get the State Premiers to agree on uniform legislation. Now, as investment houses and business leaders warn uncertainty over land title is deterring investors, Mr Keating has announced his government will use its constitutional power to force the states to adopt its legislation. Unless they toe the line, theywon't get power to veto native land use, he has warned. As the negotiations and slanging matches over this most complex and sensitive issue drag on, its potential to divide the community increases. Already this week a respected Federal Government adviser has been ordered to resign after calling Aborigines ''stone age people'' and the Australian Bankers' Association chief executive, Alan Cullen, was force to apologise for using the slur ''Abo'' in aradio interview. It is in this atmosphere of anger and division, compounded by the continuing effects of the recession, that the government has had to decide whether it can afford the tax cuts it went so far as to enshrine in law before the election. The unemployment rate jumped sharply in June, to 11.1 per cent, up from 10.7 per cent in May. In Victoria, hardest hit by the downturn, the rate reached a record 12.4 per cent. A better-than-expected balance of payments result helped official interest rates to fall to their lowest nominal level in 20 years. But the news was cold comfort for many Australians. The deficit for the financial year ending June 30 closed at A$15.3 billion and this year it is expected to worsen as demand for imports here exceeds demand for Australia's exports. The government's planned tax cuts were a key election promise - one many economic commentators said at the time it would not be able to afford. But an adamant Mr Keating said on February 9: ''The tax cuts have been legislated. They are not a promise, they are law. L-A-W.'' BUT legislation can, of course, be amended and last week, after months of speculation as to whether the cuts would be dumped, Mr Keating announced the government would bring forward cuts for middle earners to this financial year, at a cost of about A$1.2billion. but delay the rest - ''probably'' until 1998. Mr Keating's announcement on the tax cuts also foreshadowed new indirect taxes in the budget to pay for them - a move that has been mooted for some time and that has the Opposition, rejected by the electorate over its consumption tax plans, accusing the government of a back-door consumption tax. Among the revenue-raising measures tipped for the budget are: a A$30 arrival tax on tourists; a luxury tax on air tickets, meals, and hotel accommodation; higher tax on superannuation funds; death duties; and rises in indirect taxes such as sales tax. The dumping of most of the tax cuts is the highest profile and most controversial of the Keating government's broken promises but it is the latest in a lengthening list. Other broken or modified pledges include:The $A1 billion removal of old age pensioners from the tax system by 1995 - dropped. The A$30 cash rebate on child-care fees for working women - expected to be means-tested. Free dental care from July 1 for low income earners - delayed until next year. Home buyers permitted to use up to A$10,000 of their superannuation as a deposit - expected to be restricted and means-tested. A$30 allowance for women caring for children from early next year - deferred. Ten thousand private hospital beds to be ''bought'' for public patients - dropped, money to be spent differently. Overseas aid to be 0.4 per cent of GNP by 1995 - this year's allocation expected to be cut. A$130 billion in investment to flow from special government allowance - A$15 billion worth approved, government concedes A$130 billion unlikely. The Keating government's election win was generally accepted as more of a defeat for the Opposition and its goods and services tax plans than a win for the government. For those who opted for the devil they know, events since March 13 have been, if not a rude awakening, at least proof that those who warned the government's promises were hollow were right.