Mr. Trump’s comments to Mr. Comey (if true — the only source for them is a memo by Mr. Comey) do not qualify as corruption, a threat or coercion as required by federal obstruction law. A mother might make the same plea for her son, or a priest for a parishioner. Asking for leniency does not constitute obstruction, regardless of whether the crime being investigated is a violation of the Logan Act, which forbids private individuals from negotiating with foreign governments, or the False Statements Act. Mr. Trump most likely fired Mr. Comey not to thwart the investigation — Mr. Trump could have just ordered it ended, which he still has not done — but because Mr. Comey refused to affirm publicly that the president was not a target.

But even if the facts rose to the level of obstruction, most legal scholars agree that prosecutors cannot bring charges against a sitting president. The Constitution imposes on the president the duty to “take care that the laws be faithfully executed,” which vests the authority to oversee all federal law enforcement. As Alexander Hamilton observed in Federalist 70, “good government” requires “energy in the executive,” and a vigorous president is “essential to the protection of the community from foreign attacks” and “the steady administration of the laws.” Ever since the framing, presidents have enjoyed the right to drop prosecutions as a waste of resources. Indeed, this is the very theory that President Barack Obama raised when he unilaterally reduced the enforcement of the immigration laws under the Dreamers and Deferred Action for Parents of Americans programs.

Because of the original constitutional design, President Trump ultimately can order the end of any investigation, even one into his own White House. He even has the power to pardon its targets, including himself. Mr. Trump can decide tomorrow that pursuing Mr. Flynn and others for lying to the F.B.I. agents is a waste of time and money. Though he claimed that he fired Mr. Comey for not doing “a good job,” the president can fire any cabinet and high-ranking Justice Department official for any reason or no reason.

Unfortunately, the drama over the Flynn plea and White House tweeting continues to draw time and resources away from the Constitution’s one true answer for presidential corruption: impeachment and removal from office.