Your analogy just isn't analogous.

I'm not cherry picking obscure data to support a "theory".

What I'm doing is patently obvious, indisputable cause and effect.

If a kid sells orange juice by the road, but everyone buys lemonade from the kid next door, it's not gonna take very long for OJ kid to change their game.

If the republicans keep losing elections, they will move to the left to attract voters. The dems would need to move left to minimise voters lost to the republicans.

It's not a complicated theory. It's a well established obvious feature of democracy.