CANBERRA (AP) ― Prime Minister Julia Gillard put her job on the line Thursday, announcing a leadership ballot in hopes of quashing a comeback by the premier she ousted in a Labor Party coup. But Kevin Rudd’s supporters said that even if Gillard survives Monday’s vote, the turmoil surrounding her unpopular government will continue until she is out.

Rudd, who resigned as foreign minister Wednesday during an official visit to the U.S., told reporters in Washington that night that he thinks Labor will lose next year’s elections if Gillard remains leader, and that government colleagues are encouraging him to run. But he would not say whether he would challenge Gillard in the leadership ballot of Labor lawmakers until he returns to Australia on Friday.

Gillard said she will abandon her leadership ambitions if Labor lawmakers choose Rudd over her Monday, and called on Rudd to do the same if he loses.

“We need a leadership ballot to settle this question once and for all,” she told reporters.

But Rudd supporters said he would continue to destabilize the government if he lost the ballot and would try to win another ballot at a later date.

A Rudd supporter, Sen. Doug Cameron, said a Monday poll would be unfair because Rudd would not have time to canvass support.

“It’s clear that some senior ministers are intent on putting a stake through Kevin Rudd’s heart and I don’t think that’s justified,” Cameron told Australian Broadcasting Corp. television.

Gillard ousted Rudd as prime minister in June 2010 in an internal coup, and their center-left Labor Party scraped through elections later that year to lead a minority government. Polls now suggest Labor would suffer a devastating defeat, but Gillard maintains she has her colleagues’ support.

Rudd was critical of sniping against him within the party, was plainspoken about what he saw as Gillard’s dim prospects to win in a national election, and touted his own stewardship while premier of Australia’s economy during the global crisis.

“I’ve had many conversations with caucus colleagues and with ministerial colleagues. I’m very pleased and encouraged by the amount of positive support that encourages me to contest the leadership of the Australian Labor Party,’’ Rudd said Wednesday night.

He said his supporters regarded him as the best prospect to lead the ruling party to victory in the next elections and “to save the country from the ravages of an Abbot government,’’ referring to the current opposition leader, Tony Abbott.

Earlier Wednesday he had suggested that whatever Gillard’s fate is, it will be fairer than his own in 2010. “I can promise you this: There is no way ― no way ― that I will ever be party to a stealth attack on a sitting prime minister elected by the people,” Rudd said. “We all know that what happened then was wrong and it must never happen again.”

In earlier comments, Rudd left open the option of quitting politics, which would trigger a by-election and could cost Labor its single-seat majority in Parliament. That would give the conservative opposition coalition the chance to form a new government if it can win the support of independent legislators, or it could force early elections.

In apparent anticipation of a Rudd bid for the party’s leadership, Gillard deputy Wayne Swan issued scathing criticism of the former prime minister.

“For too long, Kevin Rudd has been putting his own self-interest ahead of the interests of the broader Labor movement and the country as a whole, and that needs to stop,’’ he said in a statement.

Labor senior strategist Bruce Hawker said he spoke to Rudd before his announcement and that Rudd is likely to challenge Gillard.

Before Rudd announced his resignation, Gillard had refused to comment on media reports that she intended to fire him as foreign minister for disloyalty. Rudd then criticized Gillard for failing to defend him from colleagues’ criticisms that he was undermining the government through his own leadership ambitions.

Gillard said in a statement that she was taken by surprise by the resignation, and that Rudd had never raised his complaints with her personally.

Many Australians were angry when the government dumped Rudd, who was swept into office as prime minister by general elections in 2007. In Australia’s system, the prime minister is chosen by a majority of lawmakers in the House of Representatives, not by voters.

Labor lawmakers moved against Rudd in 2010 because opinion polls suggested they were unlikely to win elections that year under his leadership.

After the 2010 elections, Labor under Gillard formed the first minority government in Australia since World War II.

Opposition leader Abbott said Rudd’s resignation confirmed that the government is unworthy to continue in office.