In the end the Social Democrats managed to get the parliamentary support of the Centre Party and Liberals (as well as the tacit support of the Left Party) by promising to implement many of their policies.
Indeed, the unstable nature of the coalition is highlighted by the fact that, even with many centrist parties abstaining, a plurality of Swedish MPs voted against reappointing the incumbent PM, Stefan Löfven (pictured), just not enough to block his appointment. Betfair is running a market on whether there will be another general election in Sweden before the end of this year, with £29,742 already wagered by punters. You can get digital odds of six (16.7%) on there being an election, and 1.13 (88.4%) on the Swedish people going to the polls again in 2019.
If this were Britain, I’d say there is no way that such an agreement could survive. But Sweden has a longer tradition of coalition governments, even minority coalitions (such as the new one). Given it took so long to negotiate, I’m sure it can survive until the end of the year, so I’d suggest you bet against a 2019 election.