STOCKHOLM (Reuters) - Sweden’s parliament will vote in early December on re-installing Social Democrat Stefan Lofven as prime minister after months of political paralysis, even though he has already failed once to form a new government.

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Long a byword for stability and consensus politics, the country has been without a new government since elections in September left the anti-immigration Sweden Democrats - with whom neither the centre-left nor centre-right wants to deal - holding the balance of power.

With both the mainstream blocs lacking a majority and unwilling to work together, parliamentary speaker Andreas Norlen said on Friday the vote would probably take place on Dec. 5, hoping to force them to compromise and avoid a fresh election.

However, Norlen was cautious on Lofven’s chances. “It is still a difficult political situation and there is, of course, no guarantee that his candidature will be successful,” he told reporters.

Lofven has been prime minister since 2014 and remains acting premier, but lost his first confidence vote in parliament after the election. Since then lawmakers have also rejected the leader of the four-party centre-right Alliance, Ulf Kristersson.

Swedish elections are often followed by haggling among the parties, but deals are traditionally struck relatively quickly, with prospective prime ministers winning confidence votes.

Lofven appealed for broad backing to break the deadlock. “I want a government that is supported across the political spectrum,” he told reporters. However, he would not comment on which parties might join a possible Social Democrat-led government.

The speaker’s options are limited if parliament, as is widely expected, votes against Lofven but Norlen is banking on a rethink before another election is necessary.

An opinion poll this week for daily Dagens Nyheter showed a new vote would not change the balance of power in parliament.

Lofven hopes to persuade the Centre and Liberal parties, formally part of the Alliance, to support a government he leads but so far they have rejected the idea.

The two parties also voted against Kristersson earlier this month, arguing his government would need support from the Sweden Democrats whose rise has shaken politics in a country that has traditionally been welcoming to immigrants.

Backing Lofven would break the Alliance but supporting a minority Alliance government would give the Sweden Democrats a chance to demand a role in policymaking.

GRAPHIC - Election scenarios: tmsnrt.rs/2p45tJh