I think if the dems really want to win in 2020 they should stop promoting the false narrative that he's unpopular. However, they really have no policies of their own to run on. Biden is still trying to hang on to the Obama years, but since things are going better under Trump that doesn't really work either (lets not forget it was the same admin who stated certain economic numbers were unattainable). They are painting themselves in a bad corner for a serious run at the White House.
https://www.washingtontimes.com/news/2019/jun/19/donald-trump-raises-record-248-million-one-day-he-/