By Ana Nicolaci da Costa and Charlotte Greenfield
WELLINGTON (Reuters) - New Zealand's opposition Labour party appointed Jacinda Ardern as its new leader on Tuesday, less than two months before a general election, in a last-minute gamble to challenge the National Party's decade-long hold on power.
Ardern took over after Labour leader Andrew Little resigned over "disturbing" opinion poll results showed the lowest support levels in more than two decades. She became her struggling party's youngest leader five days after her 37th birthday.
Analysts described the move as a potential game-changer in a Sept. 23 election that had been seen as a slam-dunk for the center-right National Party, which has been buoyed by some of the strongest recent economic growth among advanced countries.
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"The circumstances may not be what Labour has planned for this campaign, but that has not weakened my resolve or my focus or my team's resolve," Ardern told a news conference.
"I stand absolutely by the broad vision that we've presented ... the idea that everyone deserves a decent roof over their heads, a warm, dry home, access to good quality education," she said.
Ardern, a member of parliament since 2008 and a former International Union of Socialist Youth president, said she would focus on inequality and discuss a "few different ideas" with her team after taking stock over the next 72 hours.
Her message echoed the optimism that propelled Emmanuel Macron this year to become the youngest French head of state since Napoleon, and helped Justin Trudeau win the 2015 Canadian election decisively at the age of 43.
Labour also hopes that the same kind of surprise factor that saw Britain's Conservatives lose their parliamentary majority and Donald Trump become the U.S. president could rub off on New Zealand politics.
"Absolutely anything is possible," said Labour's election campaign manager Andrew Kirton.
Analysts said the stark contrast between Ardern and 55-year-old National Prime Minister Bill English could attract new voters to Labour.
Oliver Hartwich, executive director of the New Zealand Initiative think tank, said Labour had hit rock-bottom before Ardern took over.
"It will create a novelty factor, it will create some interest in the party, it will make it much harder for Bill English to campaign against her," he said.
Ardern is also vying to become the third female prime minister, after Helen Clark and Jenny Shipley, in a country that gave women the vote in 1893.
Another important factor could be whether Labour under Ardern gathers enough votes to make it a viable coalition partner, particularly with Winston Peters' king-making New Zealand First party.
"She has that X-factor and warmth a modern politician needs," said University of Otago lecturer Bryce Edwards.
"If Labour does get a boost out of Ardern ... it becomes more viable for Winston Peters to justify going with Labour after the election," he said.
Peters, who has been a senior member in previous National and Labour governments, said only that his party would decide after the election.
(Reporting by Ana Nicolaci da Costa and Charlotte Greenfield; Editing by Eric Meijer and Paul Tait)