This election, debt's only scored a bit part, which is puzzling.

In previous elections, it has been a Liberal favourite, with debt buses, giant billboards, and incessant chants of "Labor's debt".

Debt has never been a top issue with most electors, but it has been the most closely associated issue with Liberal voters, even more than the economy, at least according to our polling. It's the villain in the Liberals' pantomime.

This election, while it's still very close to Liberal voters' hearts, it's gaining more widespread appeal, being the fifth most important concept after others such as "economy", "government" and "climate change". In 2010, it was down at No 16.

One explanation for the rise is that government debt has increased as well - to more than $250 billion. Another is the Liberal Party heartland is the older voter, and older voters are more concerned about debt. They have less time to amortise it, and fewer resources to pay the interest.

If debt is more of a concern for older voters, then it should increase in importance as the electorate ages.

In 2007, when Kevin Rudd first ran for office, he was aged 50 years and two months and the average voter was 45 years and 11 months. This year, he is 55 years and 11 months and the average voter is 47 years and four months.

That's the normal rate of decay for a human being, but we're not used to seeing the average voting age decay at all.

What's more, while there will be 8 per cent more voters this year than in 2007, 67 per cent of this is attributable to the growth in voters aged 60 and over.

John Howard was an older prime minister, and not only did he pay down debt, but he set up a trust fund, the Future Fund, to pay future expenses for the kids. This is an older person's behaviour.

A German academic has created a model that predicts that rational pension reform in Germany will be impossible post-2012 because of a coupling of self-interest and an increase in the average voter's age.

That doesn't appear to be the Australian way, and while there are some who are determined to "spend the kids' inheritance", others are buying funeral plans so the kids don't even have to worry about that small expense.

Inasmuch as Labor governments prefer spending over saving, then the demographic times should favour the Liberals, apart from the general tendency to vote conservative as one ages.

However, the debt issue could also be used to motivate younger voters. Apart from finding a job, one of young Australia's biggest worries is HECS debt and a doubt of ever being financial enough to incur enough debt to buy a home.

Rental costs are so high that if the young don't live at home, they are parked in share housing.

Sooner or later, they will also realise that the structural deficit of the past seven or so years has made their situation even more parlous.

A structural deficit won't be paid back by the baby-boomers who have caused it.

Let's assume gross government debt tops out around $300bn (which could be a conservative assumption as the real cost impacts of DisabilityCare Australia and Gonski are in the out years and yet to be seen). It would take 20 years of $15bn surpluses to pay it back to zero.

Inflation will help a little, but we've never had a run of such surpluses in our history. Rudd will be well into retirement before this current round of debt is eradicated.

Which puts him well at odds with his own electorate.

Across Australia, 29 per cent of voters are 60-plus, but in his seat of Griffith it is only 17 per cent. At the other end, across Australia 27 per cent of voters are under 35, but in Griffith it is 41 per cent.

If I were the Liberal Party, I'd seriously look at running some last-minute advertising in suburbs full of young renters such as Coorparoo, Norman Park and East Brisbane, pointing out that the beneficiaries of the current government debt aren't the ones who are going to pay it back.

This article was first published in The Australian.

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