You would need to trigger a complete collapse of the American Political System.
The problem is that in US political history there's never a party that rises to national prominence that is a class based structure. From the Federalists to the Progressives there's always a cross-class membership, which combined with an individuals ability to rise up on their own (And the perception of that fact) means that without a radical transformation of the economics and politics of the country, a successful class-based party is a non-starter.
Its not just a matter of stopping Progressiveism, which is next to impossible as its not just a single organized movement with dozens of trigger influences. You would really require something much further back, a failure to ensure basic Jacksonian Democracy indefinitely until the pressure builds up enough. Which for practical purposes is impossible.