Australian Prime Minister Julia Gillard has announced a federal election for 21 August.
Ms Gillard flew from her home in Melbourne to Canberra on Saturday, where she met Governor-General Quentin Bryce to request the August election.
"Today I seek a mandate from the Australian people to move the Australian people forward," she said at a media conference.
"In this the forthcoming election campaign I'll be asking the Australian people for their trust.
"This election I believe presents Australia with a very clear choice.
"This election is about the choice as to whether we move Australia forward or go back."
Opposition leader Tony Abbott said that three weeks ago when Julia Gillard took over, the government had lost its way and since then it's only got worse.
"This election is about giving a great people a better government. We are a great country but we've been let down by a government for at least the last three years," he said.
Both party leaders have placed strong emphasis on the economy, climate change and border protection as the key issues for the election campaign.
Ms Gillard became Prime Minister on 24 June after ousting her predecessor, Kevin Rudd, when his support in the government caucus collapsed.
The coalition needs to win an extra 17 seats - or a swing of 2.3% - to get back into government.
ABC election analyst Antony Green said the leaders will be spending a lot of time campaigning in outer-surburban seats of capital cities.
"The bulk of the key seats are in New South Wales and Queensland," he said.
Police are investigating an attack on a South Australian Liberal candidate and a volunteer after the election was announced.
Jassmine Wood was handing out flyers outside a supermarket in the seat of Hindmarsh when she was approached by a man who disagreed with the Liberal Party's border protection policies.
"My poor volunteer, who was on his first day of the campaign trail, got punched in the face many times," she said.
"I got hit in the side of the head. My campaign volunteer was actually down on the ground with somebody sitting on his chest really hitting him in the face.
"The man's friend joined in, hitting my volunteer."