[Chathamization]

That's not really true. There are plenty of places where the voting system wouldn't hurt third parties (districts where one part or the other is practically non-existent, districts where the incumbent doesn't face a challenger, non-partisan races), but you largely don't see them making any progress there either.

The VPP is the most successful third party (most state reps), and it's only active in one state. The complete inability for other third parties to make almost any progress underscores the problems with the parties themselves (independents have been more successful than third party candidates).