STOCKHOLM (Reuters) - Sweden's main centre-left and centre-right political blocs are running virtually neck-and-neck just 10 days ahead of an election dominated by worries over immigration, and surging support for the populist Sweden Democrats, a poll shows.
The ruling Social Democrats are the biggest party and the centre-left bloc, which includes coalition partner the Greens, and the Left Party hold a slim lead over the four-party Alliance bloc, the poll by Novus for Swedish Television showed.
Neither grouping looks like commanding anything close to a majority with the centre-left on 40.2 percent and the Alliance on 38.9 percent.
Minority governments are not unusual in Sweden, but the make-up of the next administration remains in huge doubt because of the unaligned, anti-immigration Sweden Democrats who got 18.2 percent in the Novus poll.
In 2014, they got 13 percent, and their support was consistently under-estimated by polls in the run up to the vote. Some online surveys suggest the Sweden Democrats could now become the biggest party.
It burst onto the political scene in 2010, gaining seats in parliament for the first time. Since 2014, the party, which wants a full stop to immigration, has held the balance of power.
A deal with Sweden Democrat leader Jimmie Akesson would solve the political impasse, but he remains a pariah because of his party's past. It was founded in part by activists with white supremacist links.
Moderate Party leader Ulf Kristersson is bookies' favourite to take over from Prime Minister Stefan Lofven of the Social Democrats. But he has ruled out a formal deal with Akesson's Sweden Democrats.
Should he change his mind, he risks losing the support of parts of his own party, who ousted his predecessor after she held out an olive branch to the Sweden Democrats.
Furthermore, his Alliance partners in the Centre and Liberal parties want a return to laxer immigration policies and could jump ship if Kristersson gets too cozy with the Sweden Democrats.
Complicating the situation further, the Sweden Democrats have said they will vote down any government which does not give them influence over immigration policy.
Technically, they could side with the centre-left to prevent the Alliance taking power after the vote, but they are seen more likely to support removing Lofven in the event of a virtual tie.
None of the party leaders has given a clear answer about how they would deal with the different scenarios, leaving voters in the dark about what will happen after Sept. 9.
Weeks of horse-trading are likely before a new government is installed and prospects for an effective administration which can deal with key issues such as integration, housing and crime look slim.
(Reporting by Simon Johnson; editing by Niklas Pollard, Richard Balmforth)