"...why aren't Democrats doing more to aggressively discredit the Republican candidates?"
Good question, Kathy G...
(but is it not better to stand passionately for things that are truly authentic, creative and imaginative - like Candor ("I'm sick and tired of Republicans who simply do not care that they cannot be trusted, who are afraid of being open, and who think that honesty is for losers")- Competence (it does America no good for my opponent to remain silent in the face of his party's egregious and gratuitous lack of knowledge, experience and ability when it comes to conducting our country's foreign policy.")
You get the idea - employ the same model for Confidence, Credibility, Coherence, Courage ("if my opponent thinks that as a free citizen of this country I'm going to sit idly by while the leaders of his party cower like frightened rabbits in some dark corner thinking of ways to nullify the Constitution of the United States in the mistaken belief that that will make them safe, then he's got another think coming!") and Cheerfulness...
...all without mentioning a single Republican by name!
"It's essential that we shape the negative narratives about those bozos right now, before it's too late."
again, a good observation, Kathy G.
(... but NOT by being negative ourselves - because what we think, and how we think, we will attract and get more of...that's how human thought works.)
Accordingly, we must make what and how we think truly authentic, creative and imaginative. Besides, that's more fun than being negative - negative is for the mediocre, the shallow, the morally and practically irrelevant in our midst!
"Capitalism is the extraordinary belief that the nastiest of men, for the nastiest of reasons, will somehow work for the benefit of us all."
--John Maynard Keynes