Theoretically, a party could recognise something is needed during their first term, but feel they don't have a mandate from the voters until they've successfully been elected with it as one of their policies.

For example, if I was elected saying the tax on beer should be lower, but having met with health experts I've changed my mind and think it should be higher.

Of course, a cynic would say that's just an excuse for delaying, and a trick to play both sides...