Yes, a "moderate" Democrat can reverse course for this country but not with their current interpretation of politics. Democratic political consultants continue to ignore the obvious realities that
negative partisanship dictates elections. All elections now are influenced by national politics. Democrats are favored to have a good year in 2020, much like 2018 because of the current occupant in the White House (
generic ballot has been polling at D+6 all cycle).
The error of the Obama Administration was refusal to prosecute those responsible in the Bush Administration for their crimes. Should the next Democratic President do the same with Trump, it is only a matter of time before a more competent, authoritarian figure emerges out of the Republican Party. Liberals and conservatives speak in different languages. Conservatives operate on moral systems of punishment and reward. To curtail further assaults on democracy, the Democratic President
must prosecute all the corruption in the Trump Administration, and enact retribution towards Mitch McConnell and Congressional Republicans for their persistent attacks on Democratic norms. Such examples would be stonewalling funding to states that purge voters or requiring highway funds to come with carbon reduction requirements. Playing "hard ball" is the only language Republicans will understand, and the only way to deter future nefariousness.