We actually have a four "party" system. Even in a record high turn out year like 2020, we had about as many eligible non-voters as we had people who voted for either Biden or Trump. So we have Democrats, Republicans, Independents, and non-voters. I think that the Republicans have worked cynically for the last 40+ years to grow the non-voter section. The more they degrade norms and make politics seem corrupt and ineffective, the more it turns people off, but their angry base will still turn out.