What exactly does one do with a president who is a one-man racketeering enterprise? This question grew significantly more vexing last week, as we watched Donald Trump’s longtime personal lawyer and confidant lay out highly credible evidence that his former master had committed a smorgasbord of felonies bountiful enough to fill a first-year law student’s criminal law curriculum.

Those include bank fraud, insurance fraud, tax fraud, mail fraud, campaign finance violations and conspiracy to commit all of the above. They include obstruction of justice and suborning perjury. And, of course, depending on what Trump swore in his answers to questions from the special counsel about his Russian dealings, they include perjury itself.

If the Republican response to Michael Cohen’s congressional testimony — that Cohen was a convicted liar — seemed dimwitted, it is because it was. Of course Cohen was a liar. He was Donald Trump’s liar, employed by Trump to be his liar, deployed by Trump to be his liar, precisely because he could be counted upon by Trump to lie at Trump’s direction and for Trump’s benefit.

As of a year ago, Cohen was still the most honorable of men as far as Trump and team were concerned. When Cohen ceased to be quite so honorable in Trump’s eyes was when he ceased lying on Trump’s behalf — which just happened to coincide with the FBI’s seizure of troves of evidence from Cohen’s office, home and hotel room about what Cohen had been doing for Trump for a decade.

When, precisely, did dishonesty become a character flaw in the eyes of adherents of a president whose addiction to lying has passed from merely clinical to historic? And what, one wonders, is the diehards’ explanation for the $35,000 check signed by President Trump to personally reimburse Cohen for the hush money payments that Trump had directed Cohen to make to cover up his affair with a porn star shortly before the 2016 election? These were the hush money payments that Trump had lied about not making in connection with the affair that he had lied about not having. Is it really the Republicans’ position that the check is phony, presumably like the 10 other similar checks that Cohen delivered to Congress?

It had once seemed surreal to imagine Donald Trump indicted, arrested, tried and convicted. That is no longer the case; one now has to strain to imagine that at some point federal prosecutors will not take the mounting evidence of Trump’s criminality and do what federal prosecutors do.

Congress, however, faces a different issue, one that grows more pressing every week: how and when to exercise its constitutional responsibility for impeaching a president who has committed high crimes or misdemeanors. The Constitution does not require that those crimes or misdemeanors occur while in office, though there is already far more than probable cause to conclude that Trump committed multiple campaign-finance-related felonies while in office, and the evidence that he has committed obstruction of justice while president has grown more and more apparent. The unhappy question that looms ever larger over Congress and the American people is: Can the nation afford to have a criminal in the Oval Office, and should America be subjected to this?

The clearest takeaway from Michael Cohen’s public testimony last week is that when it comes to Donald Trump’s misconduct, we don’t yet know the half of it. Because impeachment is a solemn process, it is incumbent upon the House of Representatives to spare no effort and brook no delay getting the other half — or as much of it as can be dislodged from a White House in full stonewall mode — as quickly as possible. But at some point, it seems inevitable that the House will have to initiate impeachment proceedings, not merely because they are warranted, but also because it is its constitutional duty to do so.

Jeff Robbins is a Boston lawyer and former U.S. delegate to the U.N. Human Rights Commission.