Senator Elizabeth Warren began reading the Mueller report on a flight. She completed it after she landed and then concluded it was time to begin the impeachment process against President Trump. This is an important moment. She became the first — and so far the only — major presidential candidate to unequivocally state that the report confirmed in detail the president’s multiple attempts to obstruct the investigation into Russia’s meddling in the 2016 election and efforts by the Trump campaign, as well as its friends and family’s attempts, to cover up that effort. As Senator Warren put it, “The facts are clear: A hostile foreign government attacked our 2016 election to help Donald Trump — and Donald Trump welcomed that help. Once elected, he obstructed the investigation into that attack. If any other human being in this country did what was described in the Mueller report, they’d be in jail. This isn’t about politics — this is about principle for me. We need to protect our democracy for generations to come.”“I took an oath to uphold our Constitution, and everyone else in Congress did too. If other members think we can ignore a president’s repeated efforts to obstruct an investigation, then they should have to take that vote — and live with it for the rest of their lives.”Ms. Warren framed the impeachment question in constitutional terms because the Trump presidency has from the outset challenged the fundamental checks and balances inherent in our system of government, drifting rapidly toward autocracy. As Sarah Kendzior, a writer who specializes in authoritarian regimes, observed, Trump and his associates have publicly and repeatedly stated that the president is above the law; this is a step, a big step, toward dictatorship. Attorney General William Barr, in effect, rewrote the law in asserting that the president attempted only to derail the special counsel investigation and did not succeed and that because he did so in plain sight no crime could be charged. This is hogwash, but that nearly everyone now in federal government — elected, unelected, and seeking the Democratic nomination to run for president — has so far gone along with it is the genuine crisis.