House Judiciary Committee ranking member Jerry Nadler, D-New York, walks from Democratic Caucus leadership elections Capitol Hill in Washington, Nov. 28, 2018. Credit: Carolyn Kaster | AP

House Judiciary Committee Chairman Jerrold Nadler, D-New York, spelled out the stakes after the committee’s vote to hold Attorney General William Barr in contempt.

From a Face The Nation tweet: “We are now in a constitutional crisis,” House Judiciary Chair @RepJerryNadler tells reporters after his committee voted to hold Attorney General Barr in contempt of Congress for failing to provide the full, unredacted Mueller report and underlying documents.”

Indeed, if President Donald Trump can dream up a preposterous executive privilege claim to try to stop Barr from testifying and from producing the entire special counsel report, to prevent the star witness in the obstruction of justice probe (Donald McGahn, former White House counsel) and possibly to block Robert Mueller from testifying, we have no oversight process, no check on a lawless president and no accountability to the American people for the president’s actions.

It’s critical to keep in mind five political and legal points.

First, the basis for the Office of Legal Counsel memo has been obliterated. If the attorney general can render a judgment on indictment, but use the excuse the president cannot be indicted in office and then block Congress from access to material and to witnesses essential to consider even the possibility of impeachment, we would have constitutional chaos. A president would be motivated to break the law, the attorney general motivated to help cover it up and the president’s party motivated to help the president stonewall. If nothing else, the next president must revisit the memo (which many legal scholars think is wrong) so that at least one option is available to deal with a lawless president: indictment or Congress’ full access to materials to consider impeachment.

Second, Congress can argue with Barr, McGahn and Treasury Secretary Steven Mnuchin (who is withholding tax returns that reflect, according to The New York Times, a more than $1 billion loss over 10 years) and their lawyers for months. It can impeach them. However, the best and most effective recourse, I have come to believe, was undertaken in the emoluments case: Go to court.

Congress, as 200 members did in the emoluments case, can file a civil suit directing the president to allow Congress to carry out its constitutional responsibilities (approve or disapprove of foreign payments, investigate the president and consider impeachment). In the case of contempt, Congress can ask both for fines to be imposed (with an order that the person in contempt not receive reimbursement for the fine from the government) and for injunctive action ordering the witness to appear. It’s not swift, but neither will it take months, as some have suggested. Should Trump disobey a court order after appeals are exhausted, there would be no choice but to commence impeachment proceedings.

And that brings us to a third point: One or more of these disputes could well reach the Supreme Court. It was the court’s unanimous decision in the Watergate case, which President Richard Nixon dared not disobey, that made the tapes available and impeachable feasible. If Chief Justice John Roberts has concerns about the legitimacy of the court now, he should know that a decision enabling Trump’s lawlessness would permanently injure the court. For Justices Neil Gorsuch and Brett Kavanaugh, their votes would be a decisive moment for their legacies, an opportunity to show that they are judges, not political lackeys. (Incidentally, state bars have an obligation to make certain those witnesses who are lawyers are conducting themselves in conformity with the professional rules of ethics that, for example, prohibit making bad faith and frivolous arguments in court.)

Fourth, prosecutors in the cases spun off from the Mueller probe have a special burden: to investigate expeditiously, to preserve their records, to go to the American people and Congress if they are pressured, and then to advise Congress and the public as to their prosecutorial judgment. Likewise, the state of New York, which is not bound by the Office of Legal Counsel memo and now has a law allowing it to provide a state tax return to Congress upon request, must forge ahead and render a prompt decision on Trump’s finances.

Fifth, Democrats in Congress as well as those on the presidential campaign trail, cannot ignore this issue. They need to speak with one voice, repeatedly, about the threat Trump poses to our constitutional order. Americans need to hear why this is a big deal and why the president cannot be allowed to prevail.

Jennifer Rubin writes reported opinion for The Washington Post. Follow her on Twitter: @JRubinBlogger.