I don't quite see why the Center or Liberal Parties have to go along if they can cut a better deal.
Partly because of bloc solidarity, partly because it would screw up the 2014 elections, partly because the leadership of both parties really dislike the Soc-dems, and partly because they would never cooperate with the former communist party, whom they consider to be about as nice as the Sweden Democrats.

Another thing to remember is that the Center party is the greatest opponent of the Greens joining the centre-right, as they would occupy basically the same niche. And as the Center party kinda lacks ideology, does its best to alienate its core voters and generally just is an organisation with $300 million fortune who wants to secure jobs for its leading party members... well.

Peak oil is not an energy crisis. It is a liquid fuel crisis.