Wouldn’t this be a fourth party?
Edit: ah, “third party” is an expression in American politics. Learning something new every day.
That would still be a massive improvement. Unfortunately, the more likely outcome with our current voting system is to split the vote of whichever party they're aligned more closely with, and cause the other party to win.
We desperately need either approval voting or Condorcet voting, so that people can express a meaningful preference for a third party.
I can see ways to count > 3 (before this announcement), and obviously there are the two competitive parties so that's a way to count, but it's not obvious to me how you got to exactly 3.