Earlier quoted context omitted.
> You want third parties, you need ranked choice voting or something similar. Ranked choice or similar would only give you an occasional third party win here and there, in some small number of electoral districts. It will not give you serious and viable third parties with long living organizations. What you'd need is, proportional voting for the House. Electoral districts the size of at least 10 House representatives…
Ranked voting actually does enable third party candidate wins (assuming they can garner sufficient public support) with ranked choice voting the stigma of voting third party is removed and people can safely vote primarily for who they want instead of primarily voting strategically.
https://www.youtube.com/watch?v=JtKAScORevQ
Here's a more technical explanation by Warren Smith, a Princeton math PhD whose work was the centerpiece of the book "Gaming the Vote".
http://scorevoting.net/TarrIrv.html
Finally, see real world data from a century of IRV in Australia.