The prime minister is usually the leader of the party with the most votes, but Sweden's fragmented political landscape after Sunday's vote makes it impossible to predict who will build the next government, a process likely to take weeks.
As expected, neither Social Democratic Prime Minister Stefan Löfven's centre-left bloc nor the centre-right opposition garnered a majority – not in itself an unusual phenomenon in Sweden.
The far-right Sweden Democrats, with roots in the neo-Nazi movement, solidified their position as third-biggest party with 17.6 percent – up almost five points from the previous election – though they did perform less well than expected and have yet to shake their pariah status.
Here's the moment the first exit poll came through last night putting the Sweden Democrats at 16.3%. They eventually recorded 17.6% but the dancefloor never got going after this initial shock. #SwedenElection pic.twitter.com/g8Au35sHmw
— Paul O'Mahony (@OMahonyPaul) September 10, 2018
Far-right parties have gained strength in several European countries, including Germany and Italy. Far-right leaders in Austria, Italy and France hailed the Sweden Democrats' results.
“However the dramatic bloc battle plays out, it looks like it will be difficult for Sweden to have a functioning government,” paper of reference Dagens Nyheter predicted.
Löfven met on Monday with his party leadership to map out a way forward.
Parliamentary group leader Anders Ygeman said “it could take weeks, maybe even months” before Sweden had a government in place.
Löfven's bloc holds a razor-thin, one-seat lead over the opposition Alliance.
200,000 votes still to count
Fewer than 30,000 votes separate the blocs and nearly 200,000 ballots have yet to be counted, including votes cast in advance and abroad.
The Social Democrats won 28.4 percent of votes, down 2.6 points from the 2014 elections and their worst score in a century.
“Nevertheless, voters made the Social Democrats Sweden's biggest party,” Löfven said.
He has extended an invitation to the opposition to break the deadlock.
“We need a cross-bloc operation,” he told party supporters on Sunday evening.
— Emma Löfgren (@ekjlofgren) September 9, 2018
The four-party Alliance has so far rejected his offer, urging him to step down and make way for them to form a government.
“This government has had its chance. It has to resign,” Alliance opposition leader Ulf Kristersson told his conservative Moderate party supporters.
The Alliance was meeting on Monday to hammer out a plan of its own.
Löfven is seeking a new four-year mandate but he will have difficulty setting up a stable government. He, like the other party leaders, has ruled out any cooperation with the far-right.
He could try to build a similar government to one in 2014: a minority coalition with the Greens that relies on informal support in parliament from the ex-communist Left Party.
'Nothing will get done'
But it would be under constant threat from the Sweden Democrats, out to topple it at the first opportunity.
They are ready to block any attempt to pass legislation, such as the autumn budget bill.
Löfven could also invite the Centre and Liberal parties to join him at the negotiating table.
With one major caveat: the Centre and Liberals are members of the Alliance, together with the Moderates and Christian Democrats.
Despite their differences, notably on immigration policy, the Alliance parties that ruled Sweden from 2006 to 2014 have agreed to try to form a government together.
Why are the centre-right parties so reluctant to ally with the Social Democrats? Remember: the Social Democrats once completely dominated Swedish politics. The centre-right see their unity as the antidote.
— James Savage (@SavLocal) September 10, 2018
But that is no easy task, and the Alliance would still need the far-right's support to obtain a majority.
It would have to either make policy concessions in exchange for the Sweden Democrats' backing or offer key positions on parliamentary committees that draft legislation.
The far-right wants to curb immigration and has called for Sweden to leave the EU.
Party leader Åkesson told Swedish public radio on Monday he expected to wield major influence.
“He who understands first that he can talk to me will have the easiest time building a government,” he said.
Åkesson told daily Expressen he had invited two right-wing parties, the Moderates and Christian Democrats, to talks “to hear how they're thinking”.
“We have a long list of demands we're going to set in any negotiations,” he told news agency TT.
But Kristersson and Christian Democrats leader Ebba Busch Thor rejected his invitation, according to Dagens Nyheter.