Seriously though, there should be no litmus test for democrats outside of a sure vote against Obamacare repeal. If democrats held majorities in both houses of congress than maybe it'd be something to consider but not when every seat is important and damaging incumbents is unhelpful.
It's not something to "maybe consider": leaving even one person uninsured is a moral travesty and, when the time comes, the Democratic Party has a moral duty to implement a universal healthcare system.
A universal healthcare system and single-payer are not synonymous and you know this.