Feasibility

"No, no, no, it would never work. It would only take votes away from other viable candidates. It was always a two party system, ever since it was founded, with the Torries and the Whigs."

Woah, woah, woah, the whats and the whats? If there was never any room for a third party, then where did the Republicans and the Democrats come from? That's all just a bunch of recycled garbledy-goop -- people repeating things they heard other people say. But did they actually take time to analyze it and actually think about what they were saying?

Hmmmm....

Here is the actual real reason why it doesn't work: "Okay, the two current options are not good enough, so let's make a better option. Instead of being liberal, we'll be UBER-liberal. Instead of being conservative, we'll be UBER-conservative." And hence, the Green Party and the Libertarian Party end up being positioned even further to the right and the left. And hence, they are not viable mainstream alternatives, and so the two party hegemony endures.

Until......

The only viable way to introduce a third party is to split the middle. The only feasible alternative would be an option that is LESS liberal, and LESS conservative. This would require a political vision that is, above all, MODERATE. This is the only feasible option for a third party. Instead of being more extreme than the existing alternatives, it should be more MODERATE.

Also....

Ideally, there should be not just one new moderate party, but multiple new moderate parties. This is the only realistic way to break up the centralized monopoly of power. In order to decentralize the power structure, it is important to decentralize the power structure. Obviously. Therefore, multiple new moderate parties should compete for influence. In principle, these new moderate alternatives should be able to displace the existing dominant parties, just as the Republican and Democratic parties did in the past.