Right, back in the saddle as it were. A while ago I tore a tendon and caused a small fracture in one of my fingers playing rugby that has made typing at least awkward if not all that difficult hence the silence.
In terms of party policy I feel there are always two types of policies. There are things we simply believe in, that are part of the party's dna (see how I'm working in the title here) and are advocated for their own sake. For the Lib Dems the easiest example of this would be civil liberties, we believe they are a good thing in of themselves and therefore advocate them.
The second type is an 'objectives' policy, namely policies that we support because we believe they will have good outcomes. This covers a fairly wide variety of policies from the economy to health etc.
Of course it's more complicated than this (it always bloody is) as ways and means intertwine with each other, inform each other, and generally muddy the waters in a very unhelpful way. But it's always there, really why something is being advocated is a greater insight into a political philosophy than what is being advocated.
It's also a shifting point. It is hard to change a value that you (or your party) believe is inherently right. Once it is made into a means to an end then you can adjust it in ways you claim better achieves that end. If you're a leader of a party that has a policy of high tax rates for the sake of greater redistribution of wealth then it's hard to credibly argue that lowering the top tax rate is in line with that. It's just a u-turn.
If you first shift your argument that high tax rates are for the sake of raising high revenue then the headline policy hasn't changed, and the alteration is a detail if not just a change of emphasis. It's hard to raise passion about the change in philosophical reasoning for the same policy that you already had. Emphasise the importance of actual policy, what you actually want to do. The trick's half done in plain sight, but although people notice they don't care.
Then you can make the headline policy shift to a lower top rate tax and your line is clear, you want high tax revenue, your aims haven't changed you've just found a better way of achieving them. Flip the script and play up what you believe in as important, and that should be the trick done.
That underplays the obstacles of course, the faster you have to do it, the more awkward the particular political issue, and most importantly people trying to stop you are the fun obstacles a carefree leader attempting to rewrite his party's principles runs into. The whole point is to attempt to avoid any comparisons between stages 1 and 3. a=b b=c but if a and c are put next to each other then they're going to explode in a messy cloud of u-turn accusations.