Current deputy Nicole Manison is the frontrunner to be the Northern Territory's next chief minister after the sudden resignation of Michael Gunner.
Mr Gunner announced his decision on Tuesday, immediately after handing down the 2022/23 Territory budget.
He intends to stay on in politics and has not ruled out serving as a minister under a new leader.
Ms Manison, who has been Mr Gunner's deputy since 2016, will be acting chief ahead of a Labor caucus meeting on Friday.
Other contenders for the top job include Health Minister Natasha Fyles.
After becoming the first territory-born Top End leader, Mr Gunner attributed his decision to quit to the birth of his second son, Nash, in April and wanting to spend more time with his family.
The 46-year-old said a heart attack in January 2020, coupled with the COVID-19 pandemic had also taken a toll and he was tired.
"It has caused me to reflect a lot over the past few weeks. I've always given 100 per cent to this job and anything less is short-changing the people that sent me here," he told reporters.
"I can no longer keep looking Territorians in the eye and say 'I can keep giving 100 per cent every day', and if I can't do that I shouldn't be in the chair."
Mr Gunner said he didn't need a second near-death experience to know life was unpredictable and could be cut short.
"When I held Nash for the first time, that was it, game over. I knew straight away that I was done," he said.
Mr Gunner was first elected to the NT parliament as the member for Fannie Bay in 2008 and became opposition leader in 2015.
He led Labor to a landslide victory in 2016 before his government was returned easily in 2020, partly on the back of its handling of the pandemic.
While Ms Manison is strongly favoured to be the next chief, she batted away questions about the job, saying it would be determined by the caucus.
At the same time, she thanked Mr Gunner and said she was proud to also call him a friend.
"I think Michael will leave an outstanding legacy of being a transformative chief minister. It has been an honour. You are a legend," she said.
"Somebody who has set the foundations, economically and socially, so our kids grow up with more opportunities."
In his budget on Tuesday, Mr Gunner forecast a $1.1 billion deficit for the next financial year ahead of improved finances over the forward estimates.
By 2025/26, the deficit is tipped to fall to $17 million on the back of increasing revenue, including higher GST returns, and reduced government spending.
