Let us posit that society is at point “X” on a particular issue.
The conservative position is to conserve X.
The liberal position is to ‘progress’ to X+10.
We can posit there are some hardcore conservatives that wish to conserve X-10, the society of a few years back.
We can also posit that some hardcore liberals wish to progress to X+20.
Now we posit an overton window is accepting of the range: hardcore conservative to hardcore liberal. There are some rightests who want x-50 and some leftists who want x+50, but these are radicals and fall outside the overton window, the debate is generally kept to the conservatives and liberals, with the hardcore of each allowed a voice but being outside the mainstream.
From this we now see the range of acceptable opinion is from X-10 to X+20, while the mainstream and centrists would be be in the range of X to X+10.
Any positive deviation from X is a liberal victory and a conservative defeat. The liberals might want X+10, but X+5 is still better for them, while X+5 is still farther away from the X conservatives are conserving.
Yet the moderate opinion is almost always X+Y, it is never X-Y, and only rarely just X. So, the vast majority of acceptable choices are conservative losses and liberal gains, while non-loss is the best a conservative can realistically hope for.
The conservative will almost always lose this game.
Of course, the game is never a single competition; in real life it always iterated. In an iterated game, the conservative will always lose eventually.
To make matters worse for the conservatives, is that after the conservatives have lost, the centre changes.
Let use say the game is played and a compromise was reached, neither the conservatives nor the liberals got everything they wanted and the decision to implement X+5 was reached. After a few years or a decade or two, point X+5 has become the new norm for society, point “Y”. A conservative is now conserving point Y.
The game is now being played over the territory of Y to Y+10.
If one more compromise results in a decision to implement Y+5, it has come to the point where where liberals have obtained X+10, while the conservatives have lost completely.
As more iterations occur, society will always move towards the liberal position, with only slight slowdowns and the rare win of hardcore conservatives.
So in any political body where conservatism and liberalism are the opposed choices, conservatism is always doomed.
To not lose the conservatives have to win completely every single time. Compromise is always a long-term liberal gain and conservative loss. Any liberal win is almost always permanent, while any conservative win will likely be lost after a few more iterations.
The only way for society to not become perpetually more liberal is to make conservatism the centre. If conservatism is not the political centre, the game is always rigged in the favour of liberals.
Conservatism is always doomed.
For any society to not inevitably become increasingly liberal, reaction must always be posed against liberalism, with conservativism as the centre.
Any conservative who opposes reaction is setting himself up for a loss. Reaction is the proper opposition to liberalism, conservatism is not.
* All numbers used are arbitrary and meaningless, useful for only for illustrative purposes.