Washington — The dilemma facing House Democrats is captured by one of the most internally contradictory phrases in American legal history. In the very muddy language of the Brown v. Board of Education decision, they need to proceed “with all deliberate speed.”

Goldilocks rules again: “Not too fast, not too slow, just right.” Alas, for House Speaker Nancy Pelosi, Goldilocks never wrote a playbook for dealing with Donald Trump.

But proceed Congress must, and all who are counseling against impeachment now are overlooking the obligations of Congress that transcend politics. They want to wish away the duty of political leaders to lead, not follow, public opinion during moments of crisis. They are also misunderstanding where public opinion is moving.

And they don’t understand Trump.

The elation among Trump’s opponents when Pelosi ended months of divisive internal party debate and opened an impeachment inquiry has rather quickly been joined by worries about the implications of her decision. There are practical questions about what to do next, and some fear that Trump will turn the impeachment fight to his advantage.

The practical questions are, indeed, important, and one of them is certainly about speed. As is often the case when hard choices are concerned, both sides have a point.

If Democrats move too fast, they risk not looking deliberate and serious. They would also not give themselves time to decide whether a modest broadening of impeachment articles beyond the Ukraine matter might strengthen the case against Trump by making clear the extent and depth of his corruption.

But the slower they move, the closer the November 2020 election comes, and the more Trump’s apologists will charge that impeachment is un-democratic. Never mind that the genuinely anti-democratic acts here are all on Trump’s side: encouraging a foreign leader to intervene in that very election, hiding his skullduggery from Congress and the public, and threatening the whistleblower’s sources.

Moreover, Trump and Attorney General William Barr can be counted on to do all they can to obstruct, confuse, obfuscate, change the subject, and smear the president’s critics. The more ponderous the process, the more ineffectual Congress will look, and the more time a stunned and reeling president will have to regroup.

This is why finding a way to combine deliberation and speed, however difficult, is imperative. An impeachment process that tries to cover all of Trump’s wrongdoings would take — well, forever. Making every House committee chair equally happy is hopeless and useless. Laying out the details of the already clear-cut case against Trump on the Ukraine matter will consume enough time as it is.

So Democrats should work backward: The House should pass articles of impeachment before 2020 so the Republican leaders in the Senate don’t have an excuse to punt on the matter and say, “Let’s leave it to the voters.” Pelosi and her colleagues thus need to decide first what work can fit into a relatively short timetable, and then get it done.

Trump’s egregious behavior in trying to bring down Joe Biden by itself encompasses nearly every transgression of his presidency: lies, coverups, and the selfish misuse of power; putting his own interests ahead of our nation’s security; and an arrogant and un-Constitutional dismissal of Congress’ legitimate authority.

And here is where those who see impeachment as a political mistake miss the point. Pelosi waited until the latest revelations to act because she understood a basic truth: Nothing would be better for our country in the long run — at home and around the world — than a decisive negative verdict on Trumpism from the American people.

But given what we have learned, nothing would be worse for our constitutional system than for Congress to sit by timidly in the face of clear evidence of Trump’s desire, once again, to get foreign help in an election and his absolute indifference to the law or any of his presidential responsibilities.

Trump thrives on the weaknesses of his opponents. Like every bully, he will abuse and abuse again until someone stands up to him. For the House to back off now would send a message that the Ukraine charges are just more meaningless noise to the very voters who, if the Senate fails to convict Trump, will still have to decide his fate.

And those voters should not be underestimated. Already, the new revelations have begun to change public opinion on impeachment itself. The House’s job is to make a strong, coherent and focused case — and to trust the people’s moral sense and their reverence for our institutions.

— E.J. Dionne is a columnist for Washington Post Writers Group.