Where have you seen this happening in practice?

A political science professor first showed me 25 years ago something I still see in US national politics: a "winner-take-all" voting system that creates a polarizing dynamic, typically resulting in a roughly 51:49 split -- with the potential for radically different outcomes hinging on tiny pockets of voters.

Also, both parties are institutionally corrupted by the dominance of money (cf Lessig on "Fix Congress First", highlighting campaign finance as a fundamental threat to democracy).

But only one of the parties is exhibiting blatant, explicit, direct opposition to the principles of democracy (eg voter suppression, rule of law, etc) from the highest level on down.

The degree to which state politics are tied to the characteristics of the national party makes it difficult for powerful governors or even mayors to deviate from party lines.

Don't get me wrong; the idea of a free marketplace of ideas and the positive value of principled opposition are things I'm sure we'd agree on. But that's not what we have. Wish I knew how to fix it.