Kevin Rudd has won a leadership ballot against Julia Gillard to regain the Australian prime ministership by a margin of 57 to 45. With the September 14 election looming, Gillard’s chances of victory were deemed slim.

According to recent opinion polls, Rudd is seen as the only candidate who can potentially lead the Labor Party to victory against Tony Abbott’s Liberals in the federal election.

Gillard had promised to quit parliament if she lost the faith of the party room.

Having won the ballot, Rudd will officially become Australia’s new premier upon being sworn in by the Governor General on Thursday – the last sitting day before winter recess commences.

Embattled PM Gillard had called a Labor leadership ballot for Wednesday evening as deputies sought to depose her in favor of her predecessor Rudd. Gillard had said the loser should resign from parliament, a condition that Rudd agreed to.

Rudd said he was contesting the ballot "for the nation's sake," claiming that Labor had left the electorate with virtually no choice but to vote for Conservative opposition leader Tony Abbot, who is currently surging in the polls.

The latest national polls showed Labor’s primary vote sinking below 30 per cent. The Fairfax-Nielsen poll also shows Abbott leads Gillard by 12 percentage points as preferred prime minister, 45 to 33 per cent, adding to Labor’s sense of desperation.

However, according to an exclusive Galaxy poll for the Sunday Telegraph, Rudd could deliver a six point boost for Labor, saving up to 18 seats and delivering the party 50 per cent of the two-party preferred vote, giving Labor a real shot in the September poll.

Gillard had originally challenged Rudd for the leadership of the party in the run up to the 2010 election after the perennially-popular politician came under fire for a proposed Resource Super Profits Tax. Having lost significant support within his party, Rudd opted to resign on the day of the ballot, making Gillard the first female prime minister in Australia’s history.