In Australia, polls are tight and protest candidate support rises just ahead of national election

In their last debate before Australia's general election on Saturday, Malcolm Turnbull, the Liberal prime minister and head of the conservative coalition government, and Bill Shorten, the Labor opposition leader, faced not just an audience of swing voters, but the entire world: Facebook live-streamed the event.

An online viewer asked the first question: Given the "lies and backflipping" from major-party politicians, and the number of prime ministers Australia has churned through (five in the past decade), why should she vote for either of them? Why not vote for an independent?

Many voters are asking themselves the same thing. More than any Australian election in decades, this one could be decided by independents and small parties.

That is partly owing to surprisingly tight polls. The government's approval rating soared after Turnbull unseated the snarling Tony Abbott as the Liberal Party's leader last September. With his sunnier manner and more liberal views, many expected Turnbull to coast to victory as he sought a strong mandate of his own. But Shorten has proved an unexpectedly deft campaigner: government and opposition are now tied.

But it also shows how outmoded Australia's two-party system has grown. The class divisions that produced the Labor-Liberal divide have faded. Australia has grown more diverse and some of its concerns — climate change, immigration, China's rise — more complex.

Many voters have turned, in hope or protest, to outsider candidates, who now garner 28 percent support, according to the most recent polls. Among these the Australian Greens, an environmental party, and the Nick Xenophon Team, a new centrist party led by Xenophon, an independent senator from South Australia, are forecast to win seats in both houses of parliament.

Tony Windsor, also an independent, is challenging Barnaby Joyce, the deputy prime minister and leader of the rural National Party, for the New South Wales seat of New England. Their race shows Australia's shifting electoral dynamics. Some rural conservatives never forgave Windsor for helping Julia Gillard, a former Labor leader, form a minority government six years ago. But an unlikely alliance of farmers and environmentalists supports him.

Turnbull's pitch is simpler: Trust the Liberals to manage the economy. When the rest of the world sank into recession during the financial crisis eight years ago, Chinese hunger for Australian minerals and meat kept the country afloat. Australia has weathered the commodity boom's passing better than many expected: Growth is a healthy 3.1 percent. Interest rates are low and the currency is weak, helping investment and exports.

A poll by the Lowy Institute, a think tank, shows that 70 percent of Australians are optimistic about the economy. Turnbull, a former banker and entrepreneur, argues that his main election pledge — to cut the corporate-tax rate from 30 percent to 25 percent over the next decade — will spur investment and create jobs.

Shorten once supported similar cuts, but now wants them limited to small businesses — to which he will also offer incentives for hiring old people and parents returning to the workforce. Labor vows to match the conservatives' target of balancing the budget in four years, but admits it will run bigger deficits until then, partly because it will spend more on health and education.

Shorten says the campaign is a "referendum" on Medicare, the public health-insurance scheme that he claims the government wants to privatize. (Turnbull calls that the "biggest lie in the whole campaign".)

Otherwise, Shorten, a lawyer and former union leader, has tried to turn voters' attention from economic to social issues — particularly gay marriage. Abbott, Turnbull's predecessor, opposed gay marriage, but was grudgingly planning a plebiscite on it; polls showed a large majority would vote yes. Turnbull, a gay-marriage supporter, said then that instead of going to the expense of holding a national plebiscite, parliament should vote. But deal making with his coalition's conservatives required him to reverse his stand and agree to put gay marriage to a national vote; he "expects" it will happen this year if he wins. Shorten says that would be a "taxpayer-funded platform for homophobia," and promises to legalize gay marriage within 100 days if Labor wins.