It is fair to say that both parties supported free trade prior to 2016. In general, the Democrats thought free trade agreements should include provisions ensuring a level playing field on issues such as the protection of workers’ rights and the environment, and that industries and workers which could not survive the increased competition should be compensated, but their efforts in these areas were, in the long run, ineffective. The Republicans, for their part, welcomed free trade as a mechanism to reward both successful businesses (with higher profits) and consumers (with lower prices); businesses that could no longer compete, along with their workers, were simply dismissed as losers.
Trump changed everything with his weird fixation on trade deficits. The GOP mainstream gritted its teeth and went along for the protectionist ride. What happens now?
Free trade is one of the principal issues, along with immigration, which divides the PBP faction of the Republican Party from the Reactionaries. It is likely to be a flash point in the 2024 primaries if Trump doesn’t run again. Most of the candidates will undoubtedly follow the Trump line and support tariffs over the objections of the donor class, because there are far more Reactionaries than PBPs. My tentative prediction at this point is that a candidate who supports free trade, and has the support of the PBPs, will prevail in the primaries, largely because there will be less competition in the free trade lane.