Now we are at a point where every disagreement in politics is a personal one. This is what turned many people off to the impeachment hearings. They thought Republicans were doing the same thing. Republicans are much less adept at personal smears and even when they slip into such, they make it clear that it's the ideology that they hate more (re: Hillary).
This behavior for Democrats makes sense, though. Personal demonization brings $$$ into the campaign coffers. Unfortunately, it doesn't resonate with the public.
The Democratic party faithful is to the left of the electorate, but their donors are far, far to the left of the faithful.
The Democrats would be wiser to either ignore Bush or (like Max Baucus!) run with him.
Their donors -- global corporations -- do business with the statists and authoritarians of the world. Indirectly, it is these global statists and authoritarians who control the party.