Special counsel Robert Mueller issued a final statement on Wednesday before resigning from the Department of Justice, which clearly appeared aimed at one person: House Speaker Nancy Pelosi. Mueller’s simple message to Pelosi is that it is the constitutional duty of Congress—and her sworn duty as speaker of the House—to begin an investigation of the president and seriously consider impeaching him.

Unlike Attorney General William Barr’s early characterization of the Mueller report’s decision not to find criminal behavior on the part of the president as having nothing to do with the Department of Justice policy against indicting a sitting president, Mueller’s statement made clear the special counsel’s office believes “it was bound” by department policy not to indict the president—or even accuse him. “It would be unfair to potentially accuse somebody of a crime when there can be no court resolution of the actual charge accuse him of committing a crime,” Mueller said, reemphasizing something he had already directly stated in his report.

But coupled with this statement from Mueller were three points aimed at Pelosi: First, given DOJ policy, “the Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing.” That process is impeachment, though Mueller was again oblique about this. Second, “as set forth in the report, after that investigation, if we had confidence that the president clearly did not commit a crime, we would have said so.” Third, “when a subject of an investigation obstructs that investigation or lies to investigators, it strikes at the core of their government’s effort to find the truth and hold wrongdoers accountable.”

Put it all together and Mueller was saying: Russia interfered in our election. Trump obstructed that investigation. Mueller’s office could have said Trump didn’t commit a crime, but did not reach that conclusion. The ball is in Congress’ court. This is as close to a call for Pelosi to begin impeachment proceedings as we are likely to hear from someone as circumspect as Mueller, and it makes Pelosi’s foot-dragging not just untenable but a dereliction of her constitutional duty.

Initially, I could see reason to go along with Pelosi’s implicit argument that an impeachment inquiry against the president would be pointless if the Senate would not consider impeaching, and if public opinion was strongly against it. But the Mueller report offers substantial evidence Trump obstructed justice, and this is an impeachable offense. Members of Congress take an oath to uphold the Constitution and it is their constitutional duty to determine if Trump’s conduct merits impeachment, regardless of the political consequences. Mueller’s emphasis that this is the only way our system currently has for holding an allegedly criminal president accountable while in office points to why fulfilling that duty is more than just empty idealism. Without consequences and a full accounting of potentially criminal actions, what is to stop a criminal president from more and greater abuses of power and ultimately a breakdown of our entire legal regime?

Of course, the president should not be impeached if members of Congress conclude Trump did not do the things listed in the report, or if members conclude that the obstruction was not serious enough to merit impeachment given both the legal and political considerations. Perhaps censure is in order. But with the department and Mueller taking the position that indicting the president for crimes is off the table, an impeachment inquiry is the only way the American people will know that Trump’s potential crimes have been fully investigated and appropriate punishment considered.

No one knows if a fairly done impeachment inquiry will hurt Democrats politically. No one knows if failing to seriously pursue an impeachment inquiry will hurt Democrats more. So it makes sense to do what is constitutionally required. After all, it is not as though Pelosi is saying she doesn’t believe Trump obstructed justice or that these are not serious enough charges to merit impeachment. It seems a pure political calculation, which is arguably a dereliction of Congress’ responsibility to investigate.

If the House impeaches Trump though a fair process based on strong evidence of obstruction of justice, let the American people watch Senate Majority Leader Mitch McConnell run a sham Senate trial—with Chief Justice John Roberts presiding—and let Republican senators vote against conviction in the face of that evidence. Even if McConnell runs no trial, every senator will be asked her position on whether or not the evidence adduced by the House merits removing the president from office.

Sure that’s a political risk for Democrats, but so is doing nothing. More importantly, it’s the right thing to do as a matter of constitutional responsibility. Mueller was saying no less.