Scenarios: What will come of Sweden's hung parliament?

STOCKHOLM (Reuters) - Swedish Prime Minister Fredrik Reinfeldt's center-right coalition soundly beat the Social Democrat-led opposition in Sunday's election, but lost its majority due to gains for an anti-immigration party.

The election outcome leaves the Nordic country facing the prospect of four years of minority government, though Reinfeldt has said he will sound out the opposition Greens in an effort to broaden support for his cabinet.

A preliminary count showed the center-right Alliance bloc winning 172 seats in the 349-member parliament and the anti-immigrant Sweden Democrats 20 seats. The "Red-Green" center-left opposition was set to secure 157.

Following are some possible outcomes of the efforts to form a new government:

Center-RIGHT MINORITY GOVERNMENT

Probability: Fair chance

Failure to secure Green Party support would likely see Reinfeldt choose to continue in office in a minority government, seeking bipartisan support to pass legislation where common ground can be found and avoiding contentious issues.

Minority governments are common across the Nordic region and Sweden has been ruled by such, usually Social Democrat cabinets, through much of the post-World War Two era.

The position of minority governments was boosted after rules were changed in the 1990s, so that the government's budget bill is only rejected if the entire opposition effectively joins ranks on a comprehensive alternative.

As all parties have rejected co-operation with the Sweden Democrats, a joint vote between them and the center-left bloc seems unlikely.

However, other legislation does not carry the same caveat as budget bills. This means the government would be likely to avoid issues on which bipartisan support is uncertain, while accepting that some of its policies may be rejected by parliament.

One field where this could have repercussions in the coming months is foreign policy.

Both the center-left bloc and the Sweden Democrats have called for a rapid withdrawal of Sweden's roughly 500 troops in Afghanistan, part of the NATO-led International Security Assistance Force (ISAF), a demand opposed by the government.

Center-RIGHT GOVT WITH GREEN PARTY SUPPORT

Probability: Possible

The "hung" parliament is expected to unleash horse-trading as the center-right seeks to secure a working arrangement under which the Green Party would support its key policies in return for a say in some areas of government.

The Green Party is a relative newcomer to the center-left camp and held tentative talks on supporting a center-right bloc in the wake of the 2002 elections, though it eventually sided with the Social Democrat government.

The party's views in some areas, for instance on small business policy, are also more in line with the center-right than with the rest of the "Red-Green" bloc, but major hurdles remain for Reinfeldt's plans to enlist the Greens.

The Green Party wants to go much further than the government on a host of environmental issues, including hiking gasoline taxes and building high-speed railways in order to bring down greenhouse gas emissions faster than envisioned by Reinfeldt.

The most contentious issue is likely to be nuclear power, where the government has passed legislation allowing the construction of new reactors to replace Sweden's aging stock of 10 reactors. The Green Party wants to phase out nuclear power.

The Green Party, which has invested much of its political capital in joining the center-left bloc, is likely to need handsome political dividends, especially on environmental issues, in return for any agreement to support the government.

However, it is far from certain the Greens would demand seats in government in return for their support, something Reinfeldt would be likely to seek to avoid as he had already has to reconcile the views of four parties within his coalition.

"They (the Greens) could push for cabinet positions, but it is not certain they want to. Then they would have to take responsibility for the Alliance's policy in a different way," Gothenburg University Professor Ulf Bjereld said.

NEW ELECTION

Probability: Highly unlikely

Sweden has no tradition of holding early elections and has not held such a vote since 1958, when disagreement over a new state pension system for the Nordic country split a coalition of the Social Democrats and Center party.

Political parties on both sides are likely to be keen to avoid new elections, in part for fear the Sweden Democrats may pick up more votes after their success in Sunday's election.

This means new elections are highly unlikely, especially early in the current term.

(Additional reporting by Johan Sennero and Helena Soderpalm; Editing by Mark Heinrich)