Yes, I understand. My point is that such messaging won't be sustained. Because you would then get a classical liberal party and a left wing party that would agree with each other on social liberalism. Then policy would be made in a socially liberal direction and it would keep on getting made until society becomes, say, 20 points more liberal socially. Then there would be a chunk of the electorate that wanted social liberalism only 15 points more socially liberal. A party would want to appeal to that party, place themselves at 18 points more liberal, and would tailor their messaging to appeal to them. They would then be regarded as socially conservative by the 20 points median voters and the 22 points socially liberal party.
I have to agree. Conservatism is a moveable feast and is a relativistic one at that. That is if you are not for the progressive/change-focused policies of the Radicals/Socialists/Liberals or whatever of the 'left' then you almost by default become the Conservative party, regardless of what you call yourselves. This happened to the Girondists in the French Revolution (Also the modern Australian Liberal Party).
Having said that, there are two ways I can see something sort of like this happening but I feel that both are cop-outs.
1) Conservatives except in name
What you can have happen is the Conservatives being so utterly crushed through unpopular policies and incompetent leaders that their voters first defect on mass and are then absorbed into the faithful of the Liberals. If it's late enough this could come about as an 'Anti-Socialist' coalition party. This new bolster Liberal party would then drift to the right to retain it's new followers and become right wing party but as it does it loses some if it's weaker supporters in the centre which rebalances the party system between the Liberals and the Social Radicals/Socialists/Whigs or whatever on the left. I see it this would comprise the Classical Liberals as the dominant element but with a significant 'conservative value' voters as a minority. The name would be Liberal but the party would be slightly further to the right than a pure Liberal party.
I can see this happening in Great Britain and possibly France.
2) Revenge of the Jacobins.
This scenario involves some sort of general revolution followed by genuine elections. It would be helpful if it occurs in a way which destroys the aristocracy. The new political system would (at first) reject all vestiges of the conservatism if the old regime and only elect parties which are Liberal or more to the Left of Liberal. Presuming no successful counter-revolution, this would eventuate the situation you desired - at least in the short run, the Girondist problem I mentioned above, would inevitably occur.
I can see this happening in Germany and maybe in a unified Italy.