SYDNEY — An angry advertising campaign over a proposed super-tax is pushing usually placid Australian voters toward one of the closest, most divisive elections in memory.

Annoyed that the world's biggest mining companies are attacking his plans to extract a 40 percent tax on the profits of mineral exports, Prime Minister Kevin Rudd has opened a costly, new-style campaign to regain public support that has been badly dented by a series of humiliations.

But voters already are turning off Canberra's pre-election clashes. The latest voter survey by the respected Newspoll shows support for the Australian Greens has surged to a record high as voters turn away from both Labor and the opposition conservative coalition of Liberal-National parties.

The Greens have jumped six points in six weeks to an unprecedented 16 percent of voter support. Labor is clinging to government by 51 to 49 in a two-party preferred vote. An influential factor is an opinion poll that shows 36 percent of voters in favor of the planned minerals tax and 41 percent opposed.

Both Rudd and the opposition leader who wants to oust him, Tony Abbott, have fallen to new lows of voter satisfaction: The 36 percent approval rating for the prime minister is only one point above Abbott's.

The Rudd government has got itself entangled with its own dubious reforms in a year when the country must go to the polls to decide whether voters trust the Labor Party with a second three-year term. The latest setback is over Rudd's plans for a 40 percent tax on mineral exports, the area in which Australia excels and which has kept it above the global financial crisis.

That tax would provide a new Rudd government with a bonanza for future reforms without bankrupting a nest-egg fund left by the Howard government.

Australia is one of the few developed economies to increase export volumes amid the global crisis. Iron ore, coal and gas sales — much of which goes to China and Japan — allowed it to shrug off the world crisis.

Royalties from those exports are not enough for Canberra. Rudd has decreed a super-tax that in its first year would cut miners' earnings by 17 percent to $17 billion. World-leader exporters such as BHP Billiton and Rio Tinto, all enjoying record sales, are not amused.

The tax shocker follows a backlash to a string of political ploys designed by the government's public relations gurus to shore up sagging opinion polls. One, a world-leading carbon emissions trading scheme, has been quietly shelved in the wake of last year's Copenhagen fiasco. Voters never thought much of that anyway. What has soured public trust even more are a couple of costly blunders involving housing insulation and school building programs, both poorly supervised and becoming a bottomless pit for taxpayer dollars.

These lessons seem to have been lost on Treasurer Wayne Swan. A close friend of Rudd, Swan continues to insist his design for extracting a bigger tax slice from mineral exports from foreign and locally owned mining companies is not only overdue but fair.

When it comes to Canberra reforming Australia's biggest export industry, though, the players are far more politically powerful than homeowners and schoolteachers. Falls in mining company share prices are galvanizing the conservative side of politics.

Global stock markets have made their displeasure known. Rio Tinto, one of the world's biggest iron ore suppliers, has fallen in stock value by more than 14 percent. This is well above the 10 percent drop caused to the Australian stock market by the global finance downturn. The Australian dollar, once riding at sky-high levels, is taking a pounding.

Foreign investors annoyed by the heavy-handed Canberra decree are giving a punitive judgment. In a country built on foreign capital, this is no small deal. In a country where wage earners depend on rising stock exchange prices to raise their compulsory retirement funds, the effect easily translates to the ballot box.

Key buyers of minerals, such as China and Japan, are closely eyeing these events. These countries have invested heavily in Australian mines and want to be assured of supplies. Many Australians remember how, during a boom 30 years ago, Japanese steel mills encouraged Brazil to become a big alternative iron ore supplier because of fears of supply threats from trade union militancy.

Oddly, Rudd has handed his would-be replacement, Abbott, a sudden boost in his election bid. The still-untested Liberal Party leader has been shakily raising his opinion poll ratings. Now he is smirking as the Liberals' sagging election funds suddenly jump. Big business, appalled at the thought that corporate taxes may be next on Labor's hit list, are returning as the traditional source of conservative parties' fighting funds.

Their hopes reviving, the Liberal-National coalition is starting to sound confident for the first time since longtime Prime Minister John Howard lost his parliamentary seat three years ago. The coalition is looking hard at Abbott to see if he can capitalize on the new change of fortunes.

Malcolm Turnbull, the Howard successor that Abbott defeated by one vote in a party leadership spill, is waiting in the wings. Turnbull, a former lawyer and merchant banker, is a proven force. He has reversed his decision to retire from politics, seemingly with an eye to leading his party again if Abbott fails to pull off what will be a close election

Still, nobody is writing off Rudd. The former diplomat and party apparatchik is a smooth operator. But some in his own party are running scared. In the Sydney-based party, former minister Michael Costa has accused Rudd of breaking a promise, and is calling his party "dysfunctional."

Until recently Rudd had enjoyed a long honeymoon with the media. Now the television cameras have turned away. Canberra watchers sense that an "all bets off" campaign will be the prelude to the election.

Alan Goodall is former Tokyo bureau chief for The Australian.