Strange as it might seem, there is a bipartisan pitch in this election campaign. Both the Prime Minister and the Opposition Leader have projected their optimism for Australia. On Sunday afternoon, Kevin Rudd declared: “Ours is a truly great country; nobody should ever talk this country down.” Soon after, Tony Abbott stated: “Our best years are ahead of us.” He added the rider “but only if we seize our opportunities and one opportunity we must seize is the opportunity to change the government”.

That's the essential difference between government and opposition. The former wants to project optimism with a minimum of self-criticism. The latter, however, attempts to blend optimism about the future with criticism of the status quo. Oppositions have to criticise governments – otherwise there would be no need to change administrations.

Labor has been obsessed with Abbott ever since he became Liberal Party leader in December 2009. Confident leaders in democracies tend to downplay the importance of their opponents. Not in contemporary Australia. For the past four years, first Rudd, followed by Julia Gillard, followed again by Rudd, have constantly focused on Abbott. In particular, his alleged negativity.

On Monday, the AM program led with a 13-minute interview with the Prime Minister. He referred to “Mr Abbott” on 16 occasions – more than once a minute. Rudd's line was that Abbott represented “the old politics of the past … which is grounded in negativity”.

No doubt Labor's internal polling is suggesting Abbott's alleged negativity is one of his vulnerable points. The tactic may or may not work. However, the fact remains that all successful opposition leaders criticise incumbents. And it is easy for governments to pass off criticism as negativity. To accept Rudd Labor's critique of Abbott, you have to accept that all disagreement is negative. Some is. Some is not.

Negativity is best measured with respect to the past since empirical evidence exists as to outcomes. Here there is a tendency among social democrats and leftists alike to condemn Australia during the time when it has been led by the political conservatives – now the Liberal Party-Nationals Coalition.

On Sunday, Rudd said that Gough Whitlam's free tertiary education policy, introduced in 1973, ''made it possible for a kid from the Queensland country, neither of whose parents went much beyond post primary school, to go off to university”. The implication here is that, in the 1950s and '60s, only the sons and daughters of the wealthy obtained tertiary education.

Not so. In 1951, the Robert Menzies-led Coalition government initiated the Commonwealth scholarship scheme, which provided free tertiary education plus a means-tested living allowance. A bright student, like Rudd, would almost certainly have benefited from the scheme. The idea that the poor were deprived of tertiary education before Whitlam is but a myth. And negative.

This was very much the theme of Whitlam: The Power & The Passion, written and directed by Paul Clarke, which aired on ABC 1 recently. Despite being advertised as the “definitive” documentary on Gough Whitlam's government, it contained numerous howlers. This is standard practice for ABC documentaries.

Clarke's narrator and his chosen left-wing commentators condemned Australia in the Menzies years as out-of-date, subservient, asleep at the wheel and so on. According to Clarke, before Whitlam, Australia was a “bogan underworld”.

The self-proclaimed definitive documentary dismissed or ignored all the changes introduced by the governments led by Menzies, Harold Holt and John Gorton, which had made Australia such a successful nation before Whitlam became prime minister. Clarke regards the successful government of Labor's Bob Hawke as less impressive than the shambles over which Whitlam presided.

Rudd himself has criticised Australia during the time of Hawke and his treasurer, Paul Keating, who, in turn, became prime minister in 1991. In his Howard's Brutopia article, which was published in the November 2006 issue of The Monthly, Rudd criticised the “free-market fundamentalism” of Howard. But this was only an extension of the Hawke-Keating economic reform agenda. A year later, Rudd declared that he was an economic conservative – just like Howard.

When Rudd wrote his Brutopia essay in 2006, Australia was a remarkably successful nation – as it remains today. It is understandable that Rudd was critical of his then opponent. But his criticism of the economic reform process of the 1980s, 1990s and early 2000s was a manifestation of negativity. If he wants us to be positive about Australia, he should not be so negative about the past.

Gerard Henderson is executive director of the Sydney Institute.