In their book The Party Decides: Presidential Nominations Before and After Reform, Cohen et al. argue that there is a direct correlation between the amount of time a party has been out of the office and the centrism of their platform:
[T]he longer a party is deprived control of the White House, the more moderate its presidential nominees become. One term out of office may be a fluke, but two terms is serious, and three is catastrophic. Parties take this seriously and tend to nominate considerably more centrist people, sacrificing a significant chunk of their governing agenda for a chance of actually governing.
I would suppose the same holds true for other countries as well…
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Reactor Fire 