The first steps to form the next Government were taken on Sunday when NZ First held separate meetings with National and Labour.
With kingmaker Winston Peters at the table, negotiating teams headed by Prime Minister Bill English and Labour leader Jacinda Ardern began vying for NZ First's support.
Final election results, released on Saturday, confirmed neither National nor a Labour/Greens alliance can command a parliamentary majority without NZ First.
Each meeting lasted two-and-a-half hours and almost certainly involved policy concessions Mr Peters wants in return for NZ First's backing.
The three parties have agreed the negotiations will be strictly confidential, and the leaders had little to say after the first forays into Government formation.
Mr English emerged several hours after his meeting to say "negotiations went just fine, thanks".
Ms Ardern described Labour's meeting as "excellent and productive - negotiations will continue with the parties we are looking to form a stable, durable Government with."
Mr Peters said the talks had been very constructive but would continue for some time, picking up again "all day [Monday] and into the night".
The NZ First leader said there's nothing to suggest he won't have a decision by Thursday - a very tight deadline - and there are reports of behind-the-scenes activity which could clear up the details of policy agreements.
All three parties have carried out intensive preparatory work and senior MPs are said to have been talking to their counterparts as their leaders handle the top level negotiations.
The talks have been about policy not ministerial postings.
Mr Peters said there were "a number of serious policies top of our list".
All nine permutations for forming Government remain on the table.
"If you don't keep your eyes wide open as to all the possibilities you may have missed a great chance for your country, for the country's social and economic progress," he said.
Sunday's negotiating teams were much the same as those that handled preliminary discussions last week.
Mr Peters had his deputy Ron Mark, MP Tracey Martin, confidante Paul Carrad, chief of staff David Broome and staffer Kirsty Christison.
Mr English kept senior ministers Gerry Brownlee and Steven Joyce and his chief of staff Wayne Eagleson but added deputy Paula Bennett to the team.
Ms Ardern made just one change to her team line-up, switching out former deputy prime minister Sir Michael Cullen for former deputy leader Annette King.
Others on Ms Ardern's team were MP Grant Robertson, strategic adviser Mike Munro and chief of staff Neale Jones.
The meetings took place in a neutral venue at Parliament, where they're expected to continue on Monday.
Green Party MPs, including leader James Shaw, have been at Parliament, but are not directly involved in negotiations with NZ First.
Mr Peters had not wanted to begin any serious discussions until after special votes had been counted and each party knew how many seats it had.
That was settled on Saturday: National has 56, Labour 46, NZ First nine, the Greens eight and ACT one.
The Opposition parties are in a stronger position than they were on election night when Labour, the Greens and NZ First had a total 61 seats - a bare majority of one vote in the 120-member Parliament.
Now they have 63 against a total of 65 for a National/NZ First combination.