Demand for advertising inventory across a range of media increase once the election campaign officially gets under way in the middle of May.

Non-political advertisers will already be mulling over whether they want to hold off on their own ads or pay the increased rates in a suddenly crowded time period.

"Advertisers will start to second-guess as we lead into those key dates," chief executive of media agency PHD Mark Coad said.

Mr Coad said that some advertisers may look to move their campaigns if there is an influx of political party spending, while others may keep going with business as usual.

Government ads decline

Once an election is called, caretaker conventions are installed for governing until a new government is elected. Government-funded advertising that is seen as political is suspended, while non-controversial government advertising, such as defence force or public health, typically continues.

The Department of Finance and Deregulation reviews all government advertising campaigns at the start of the caretaker period and recommends which should be deferred or continued. For example, it would review the government's "ideas boom" campaign to determine whether it was political or not.

Mark McCraith, chief executive of media agency Maxus, said political parties will use mass media, such as television, to set up a big national blueprint.

However, the parties will figure out which seats they need to win and are marginal and target them at a grass-roots level with local advertising such as pamphlets and geographically targeted social media, he said.

Happy networks

"I think the TV networks will be happy that it's coming, plus they've got a census, plus [Seven] have got the Olympics. They'll get an injection of cash. The question will be how much of the percentage of the budget will be spent on TV," Mr McCraith said.

"I wouldn't be surprised if both parties have locked base TV schedules already."

oOh! Media chief executive Brendon Cook said that his company had been taking bookings from political interests groups for nearly four weeks, with a lot of interest in the final weeks before July 2.

Signage on government land, such as bus shelters, traditionally can't take political party advertising and the individual property owners where other signs are located regularly stipulate that they will not take political ads in their contracts, Mr Cook said.

"We have space that we can sell political parties and more of that gets taken up pretty quickly. But obviously we couldn't maximise the power of the medium and its value to political parties because of the restrictions that are placed on us," he said.

Billboards are limited

APN Outdoor chief executive Richard Herring said despite the limited stock there is a place for outdoor advertising in the federalelection campaign, especially with digital signage.

"Typically election advertising has been one where messages have changed ... digital can change message immediately," Mr Herring said.

Greens leader Richard Di Natale has already begun to tap supporters for donations to buy billboard advertising.

"Right now, every campaign manager, for every political party, is racing to lock in their TV and radio ads and to snap up billboards in high traffic areas," he wrote to supporters early last week. "Will you make a donation today so we can beat them to the chase and lock in our advertising before the Labor and Liberal parties get in first and outspend us?"