On the afternoon of Oct. 8, the White House sent a letter to House Democrats describing the ongoing impeachment inquiry as “constitutionally invalid and a violation of due process.” This followed the Trump administration’s decision to block Gordon D. Sondland, the ambassador to the European Union, from testifying before Congress earlier that day about his discussions with other U.S. diplomats regarding President Trump’s attempts to pressure Ukraine to conduct investigations that would be to the president’s political advantage.

The administration’s full-court press to stonewall the House’s inquiry only underlines the necessity of hearings, evidence and testimony to establish a full accounting of the facts. The details of Mr. Trump’s call with the president of Ukraine, overlapping in time with the delayed release of congressionally authorized military aid, raise concerns about a possible, deeply disturbing misuse of presidential power, which can only be resolved by a full investigation. While enough facts are still unknown that a decision on impeachment itself is premature, an inquiry is absolutely necessary.

The administration’s full-court press to stonewall the House’s inquiry only underlines the necessity of hearings, evidence and testimony to establish a full accounting of the facts.

Yesterday’s letter by the president’s legal counsel contains no convincing objection to such an inquiry. The letter claims that an impeachment inquiry must be authorized by a formal vote, but this is neither constitutionally nor otherwise legally required for the House to hold hearings or subpoena witnesses. Since the administration has already frequently refused to cooperate with congressional oversight even when unconnected to any potentially impeachable matters and declined yesterday to commit to cooperating even if an inquiry is formally authorized, this sudden assertion of an imaginary constitutional requirement rings false.

Neither is there any requirement at this early stage for the president to be able to see evidence in advance and cross-examine witnesses during a process which the Constitution entrusts to the “sole Power” of the House. House committee proceedings already allow both parties to make their concerns heard, and an impeachment inquiry is analogous to a grand jury proceeding, not a trial. If the House does not, during the full course of the inquiry, make sufficient allowance for the president to present a defense, then the proper remedy is for him to do so in the Senate trial that would follow a vote to impeach.

Instead, the letter accuses House Democrats of seeking to overturn the 2016 election and shockingly concludes that the president “cannot allow [the House’s] constitutionally illegitimate proceeding to distract him” and will therefore refuse to cooperate with the inquiry. In fact, such a manifestly absurd dismissal of a co-equal branch of government is itself an alarming overreach of executive power, which itself amounts to a rejection of the 2018 election that gave Democrats a majority in the House.

Nonetheless, even though its power to exercise oversight, investigate and call witnesses does not depend on it, the House should formally vote to open an impeachment inquiry. While Mr. Trump has no authority to require it of the House or to refuse cooperation without it, such a resolution would be helpful and prudent for many reasons. A House-wide vote to authorize an impeachment inquiry would follow the precedents established by the Nixon and Clinton impeachment inquiries, reaffirm the House’s constitutional responsibility in the impeachment process and make it even clearer that refusal to cooperate with the inquiry is itself an affront to the constitutional order.

The apparent reasons that Democrats have not yet held a formal vote are underwhelming: the desire to spare vulnerable members a politically costly vote and the additional concern that Republicans would in turn demand subpoena power, which they could use to pursue the smokescreen allegations of misconduct on the part of the president’s opponents contained in the administration’s letter. Those risks are far outweighed by the benefits of embracing the House’s constitutional duty and requiring all its members to go on the record as to whether Mr. Trump’s apparent use of foreign policy for his personal political advantage and his manifest disdain for the system of checks and balances warrants a House-sanctioned investigation and possible impeachment.

This article appears in October 28 2019.