If the two party system consisted of the Libertarians and the Greens...

[progressive85]

If you took out most of the socio-cultural issues on issues like sex, gender, and reproduction that dominate today's political climate, and have a consensus on race (that we're all raised to be truly colorblind), and make politics more about economic issues, you would get to this faster.

In the first election, I could see a Libertarian victory based on the desire for people to have job industries thrive and also because people want less taxes and do not agree with "Big Government" ideas.  The Green Party would have pockets, but I can't see them doing that much better than they already do now.  Honestly not enough people care about the environment to the point where they'd base their whole way of thinking on it.

That changes if people start to connect economic losses to environmental damage, and then swing voters begin to move towards Green ideas for the economy, which means higher taxes on the rich and big investments at the federal level (a Green Great Society).

To get to a Libertarian vs. Green realignment, you first need to move past the social and cultural issues though.  The religious right needs to lose its power.  The identity movements need to fade away.  I can't see, in the America of 2023, this happening tomorrow, but maybe in the 40s or 50s/mid-century.