Correlation is not causation. Sure, people who are wealthier and live in more stable societies tend to vote Democrat; but that doesn't mean that electing Democrat representatives causes the societies to be wealthier and more stable. Working hard and being wealthy are also correlated, but that doesn't imply that you can cause people to work hard by giving them lots of money. (Lest anyone accuse me of political bias he…
Your first line is a truism that your main argument doesn't support, and your third paragraph is an appeal to "common sense" that isn't supported by data. Ignoring those, your argument boils down to your opinion that voting has no impact on wealth or stability. That cannot be true, at least not unless you subscribe to a deterministic world view, surely?
One could imagine a scenario where a Party X state had vastly impoverished natural resources compared to the typical Party Y state. It's conceivable that typical Party Y policies would have a worse outcome than typical Party X ones in that particular state, even if states that implement Party Y policies tend to have better outcomes overall. It's furthermore conceivable that even states that implement Party Y policies could do better if they had instead implemented Party X ones.
The flaw in this article isn't political, it's statistical.
edit: anonymized parties in the second paragraph.