Interesting analysis. And historically your comment that the "minority" party will inexorably be dragged leftwards is also correct as seen from the Swedish perspective. However, when the change eventually came, it came via a true conservative who got fed up with the timid party hierarchy and took over the party leadership in something of a coup.
His message eventually (and continuously) helped to unset the almost unbeatable social democrats. But it took more than 2 election cycles, and even then it took another few election cycles to safely post the conservatives at a level between 20 - 25%. (Coalition governments are very common not only in Sweden but most European countries with a proportional voting system.)
Note, however, that the change in Sweden took place during the red 70s, a coupleof years before Reagan and Thatcher transformed the international standing of conservatism.
As I understand it however, they took similar positions to those of the Social Democrats. The only party that seems to actually hold conservative views would be the Sweden Democrats (whom I am hoping will one day liberate their land).
Thanks for the historical information re: Swedish politics.
How conservative is Sweden today in your estimate?