Bringing up certain bogeymen (or bogeywomen) in an effort to increase fundraising and voter turnout has been done by both parties in the past.
After all, Obama ran against George W Bush TWICE in the '08 and '12 elections despite the fact that Bush's term ended in '08. The '08 election was basically a referendum on Bush's term in office, and Obama repeatedly compared his '12 opponent Mitt Romney to Bush and insinuated that voting for Romney would be like voting for a 3rd term for Bush.
If you go back and watch the 2012 debates, an actual question that was asked by one of the debate moderators first to Romney and then to Obama, was literally "how are you / your policies different from that of George W Bush?" Now imagine a debate moderator asking whoever Trump's opponent in '20 is "How are you different from Hillary Clinton?" It would never happen.
I would beg to differ with this comparison: George W. Bush was actually our president at one particularly dark point in our history. Hillary Clinton was never president. Suggesting that the two persons have legacies of the same historical significance seems a little silly to me.