There are two reason that democrats don't want to impeach. The Republicans won't impeach Trump for serious crimes against the nation but impeached Clinton for lying about sex on an instance where they happened to have turned up a completely unrelated discovery of a blue dress. They had the philandering asshole by the nuts and their craven attempt to nail him to the cross turned out to make the public sick. They always reveal themselves to be righteous swine just as they are now with their criminally blind Trump support for an immoral pig beautified for them by being painted with their favorite team brand lipstick.
So now that the Republicans polluted the impeachment waters and paid a price, the democrats, who wouldn't impeach then can't find the guts to impeach now, the moral weight of the sins of Trump compared to Clinton making no earthly difference. Thus does the moral core that once made us great dissipate to utilitarian concerns. Morality and the oath of office, the duty to hold the President accountable, fly out the window because of ideologically, things don't look promising.
But there is a truth and everybody knows it at an unconscious level, and that truth is that Democrats have a moral duty to impeach Trump whatever the price. There is the practical which will not admit of the presence of one's immortal soul. Those who do not know their true center will always wonder morally lost. There is one power that will never go extinct so long as children are born, and that is the hunger for justice. I say if you want to win elections make your appeal for that and then deliver.
Garbage like Trump exist because it's costly to oppose him. Better to go with the flow said the jelly fish.