Healthcare is the most tenable (populist) strategy for midterms and 2020
This may sound simplistic, but simple is what we need. Russiagate is not gaining any sort of traction with the right. In fact, I would go so far as to say it creates more of a barrier to those who would otherwise support a Democrat healthcare plan.
Furthermore, this populism that tRump ran on became a sticking point even for the left. We would not have had this b.s. discussion about "elitism" if it hadn't been for the right wing narrative about caring for the poor and middle class average Joe (please, let's not start arguing that again! I include it here merely as reference to how compelling the rethug narrative was). However, as many, many poor and middle class average Joes have seen in the last few months, that populist rhetoric was a blatant lie. We need to dwell on that lie, bring it to the surface and discuss it at length as a means to turn voters toward Democrat candidates next year.
Perhaps this could be a wedge issue that drives more voters into the light. While I am certainly not advocating for extending an olive branch to deplorables, some might come to realize how corrupt the right is on their own. At the very least, focusing on healthcare will motivate voters more than any other issue.