Single payer is a very, very hard concept to sell to the conservative and moderate middle class. The ACA was only passed on repeated campaign promises that if you like your health insurance and health care then you can keep it and the GOP's continual alternative facts have convinced many that the ACA is awful and was the wrong thing to do. It was likely one of the principal issues that caused many swing voters to back Trump even though they hated him personally. With that being said the GOP has not started out their president, senate and House trifecta with popular legislation and could get brutally beaten in the next two elections. It might be possible to sell single payer in the next election cycle to an increasingly liberal voting block though. It would almost certainly hurt their election numbers overall even if it could help them in the long run. The help would be a fairly successful health care system that covers everyone.