Former Australian Prime Minister Kevin Rudd has entered the election campaign with a stinging attack on the opposition Liberal leader Tony Abbott.
In his first appearance since being ousted as leader, Mr Rudd said he would back Julia Gillard - the woman who deposed him in June.
The Labor party has suffered a slump in popularity in recent weeks.
Mr Rudd said he would not stand "idly by" and watch Mr Abbott "slide quietly into office" in the 21 August vote.
Mr Abbott, leader of the Liberal Party, the main partner in the conservative-coalition opposition, is hoping to deny Labor a second three-year term.
He remains the underdog in opinion polls - but only by a small margin. He has attacked Labor's "great big new tax" on big mining firms and pledged to "stop the boats" bringing asylum-seekers to Australia.
Prime Minister Julia Gillard came to power in June after senior Labor powerbrokers - concerned by weeks of poor poll ratings - told Mr Rudd he had lost their support.
Ms Gillard's challenge for the leadership came amid fears that Mr Rudd could not win a second election.
His sudden and unexpected ousting has created divisions in the party.
The initial surge in public support enjoyed by Ms Gillard has been dented by a series of government leaks to the media, which are suspected to have come from Mr Rudd or his supporters.
Ms Gillard is accused of going back on a secret deal when she challenged for Mr Rudd's leadership.
Other reports say she unsuccessfully argued in closed-door cabinet meetings against increasing pensions because old people did not vote for Labor.
Mr Rudd, who has denied responsibility for the leaks, told reporters at a news conference that the infighting was distracting voters.
"There is a real danger at present because of the rolling political controversy about myself, that Mr Abbott is simply able to slide quietly into the office of prime minister," said Mr Rudd.
He said he would not "stand idly by and watch Mr Abbott try to slide into office by default without any real scrutiny being applied".
He said: "Life's too short to carry around a great bucket-load of anger and resentment and bitterness and hatred."
Mr Rudd, who is recovering after having his gall bladder removed, said Ms Gillard had asked him to join her election campaign.
He said he would begin canvassing next week in his home state of Queensland and in New South Wales.
Ms Gillard said she welcomed her predecessor's support. She has offered Mr Rudd a senior position if Labor is re-elected.