In the lower bodies of legislatures, there will be 15 independent or third-party representatives, which puts the major-party percentage at 99.72%. Of those 15, 8 come from Vermont.
That level of two-party domination is remarkable, particularly given that in November 26% of voters described themselves as independents. But, even independent-minded aspirants for office seem to accept that a major-party affiliation will help them get elected and help them advance their priorities once they're in office. That's especially true in legislative politics, where voters often know nothing about the candidates other than the party they represent.