The proverb "when you strike at a king, you must kill him" is attributed to Ralph Waldo Emerson, but Emerson was expressing an idea that goes back at least to Machiavelli, who advises in The Prince that "men ought either to be well treated or crushed, because they can avenge themselves of lighter injuries, of more serious ones they cannot; therefore the injury that is to be done to a man ought to be of such a kind that one does not stand in fear of revenge."
It is advice that the Democrats have completely ignored in their impeachment spectacle, to their peril. There was never any chance that Trump was going to be removed from office, and rather than harming him politically it has elevated his approval rating to a personal best of 49%. (Which is, to be sure, still abysmally low, but we all should have learned that between the Electoral College and voters uninspired by awful Democratic candidates, he does not need approval by more than 50% of the country to remain in power.)
The political incompetence of the Democrats has been highlighted this news cycle by the debacle in Iowa, by the DNC's last minute rule change to enable Michael Bloomberg to participate in debates, and by Nancy Pelosi's public temper tantrum at the State of the Union, tearing up Trump's speech.
Trump's whole brand is "I am fighting these Washington insiders and they hate me for it," and the Democrats just keep walking right into it. I fully expect footage of Pelosi's paper tearing to show up in a Trump campaign ad.
The Republicans are driving the country off a cliff; the Democrats offer nothing but slowing the car down slightly, and then prove unable to take the wheel from the Republicans. We must break open the two-party system -- not at some future date, but immediately. Buying into Democrat's story that "oh, yes, it would be good to have more parties but we can't afford that now, This Election Is Too Important To Vote Your Conscience" is how we ended up in this position.
Even if the Democrats nominate Sanders -- and sadly it looks like the DNC is pulling out all the stops to prevent that -- if you live in a deep blue or deep red state your vote for him in the general election would be wasted. (It does not matter by how many points the Dems take Maryland, they get the same number of electoral votes.) Use your vote to help crack open the system. We cannot afford this status quo any longer.