What will happen election day and beyond?

In this last week of the election campaign, when the picture should be clearer, I have been asked by numerous inquisitors who I think will win on Saturday: Malcolm Turnbull or Bill Shorten. Having been directly involved in more than 10 federal and state election campaigns, my considered response after examining the polls and the betting is: I don't know. While the sheer size of the Coalition's majority makes it favourite, in all walks of life and in all sports, favourites get beaten.

Turnbull or Shorten will lead a party that wins enough seats to form the next Australian government – a big prize and an even bigger responsibility – but there is so much disenchantment with "big politics" that soft voters would prefer a third candidate. Business is anxious that the prime minister will not be able to claim a mandate to make the hard decisions the nation needs, especially when a double dissolution guarantees a Senate crossbench of around the same size as that of the previous parliament.

When voters are raging against the machine, it is the incumbent who is in the greater danger. How do we know? In the 1998 Queensland state election, Pauline Hanson's conservative One Nation Party received 22 per cent of the state vote, stripping 4 per cent from the Labor opposition but more than double that from the ruling Liberals and Nationals. Although One Nation won 11 of the 89 seats, the Beattie-led opposition won government, removing the Borbidge government after just one term. The more Pauline Hanson, then a federal member of parliament with the initials "MP" after her name, declared she was not a politician, the louder her supporters cheered.

If there were a national, charismatic political figure contesting the 2016 election on a platform of busting open the two-party system, he or she would do very well. How do we know? Watch the Xenophon vote in South Australia tomorrow night. He will have up to four senators elected, is a good chance of winning the Liberal seat of Mayo, and may cause another upset or two in the lower house. Since his pitch is to break up the two-party duopoly, he doesn't really need a policy platform.

At the 2013 federal election, Clive Palmer won a safe federal seat from the Liberals and his Palmer United Party gained three Senate positions. Most of those who voted for Palmer's party did not truly consider he had a wonderful policy manifesto. Rather, he was a big, loud anti-establishment, anti-Canberra personality.

From this it would be easy to conclude that the next parliament will be as unwieldy and dysfunctional as the last. In his final pitch to voters on Friday, Turnbull called for greater civility in the house. Putting aside that Tony Abbott in 2010 pledged a "kinder, gentler polity" and delivered a vicious opposition obsessed with personality politics, Turnbull's call is worthy and noble.

But can it be achieved? Australians have long been sick and tired of bitter rancour in the parliament, but that hasn't been a major deterrent. However, this time around the external economic environment will be ugly, imposing a sense of economic crisis on Australia. Australia's AAA credit rating is at risk.

Whichever side wins government will need to do much more budget repair work than the official forecasts imply. Both parties have had to rely on the official numbers; there is no alternative. But those forecasts are wrong and the authors – the secretaries of the Treasury and Finance departments – admitted as much in their two-page commentary in the pre-election economic and fiscal outlook.

When this is confirmed in the official briefs for the incoming government and opposition, the government will need to bring down a mini-budget, announcing further expenditure cuts and revenue measures. As long as those measures do not blatantly break election promises or cause great hardship to the poor, it will be exceptionally difficult for the opposition to block them in the Senate. To do so would open up the opposition to accusations of economic vandalism, of destroying Australia's coveted AAA credit rating that both sides have pledged to protect.

This campaign has been civil. Neither Turnbull nor Shorten is a political head-kicker. It's a big call, but there is a very good chance that whichever party wins on Saturday, the Australian people will witness a return to civility and a constructive national parliament.