The only thing that comes close to a left wing part of the Republican Party is Sue Collins, who is always very sorry and disappointed but eventually toes the party line.
Compared to Trump, roughly half of the Republican party is to his left by varying magnitudes. Obamacare, for example, was originally a Republican proposal.
But yes, the entire Republican party line eventually toes the party line. Same for the Democratic party, as long as the party line strengthens the class interests of the elite.
