Donald Trump is suddenly enthusiastic about one of the more obscure powers associated with the presidency. The Constitution says that the executive “shall have Power to grant Reprieves and Pardons for Offenses against the United States…”

A desperate and embattled Trump is now reading this phrase in the broadest possible sense, claiming in a Saturday morning tweet that “all agree the U.S. President has the complete power to pardon.”

As it happens, all do not agree.

Trump’s Nixonian assertion has opened up a robust debate about whether a president—especially a president plagued by the sort of scandals that swirl around this White House—could pardon himself. After The Washington Post reported Friday that the president might be considering just such an abuse of power, University of Michigan Law School professor Richard Primus wrote: “A self-pardon would be something new in American history—and just the kind of departure from prior norms that typifies Trump. The Constitution doesn’t specify whether the president can pardon himself, and no court has ever ruled on the issue, because no president has ever been brazen enough to try it. Among constitutional lawyers, the dominant (though not unanimous) answer is ‘no,’ in part because letting any person exempt himself from criminal liability would be a fundamental affront to America’s basic rule-of-law values.”

“But as a practical matter, it’s not a panel of legal experts that will decide this issue,” Primus explained in a primer that appeared on the Politico website. “It probably won’t be a court, either. Instead, the answer will be fought out at the highest levels of American politics. And in real life, if the president signed a document with the words ‘I pardon myself’—which he certainly could—it’s impossible to know what would happen next.”

Actually, it is quite possible to know what should happen next. The framers of the Constitution were clear about that.

The full section of the Constitution dealing with the pardon power—Article II, Section 2, Clause 1—declares that the president “shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.”

In other words, a president cannot pardon himself out of impeachment. That’s because impeachment is not a legal procedure but a political act.

The power to impeach a president (or a vice president, or an attorney general) rests with the US House of Representatives. If the House impeaches a president, he is tried by the Senate. If convicted, the president is removed from office.

No pardon can interrupt the process.

No pardon can alter or reverse the Senate’s decision.

Donald Trump may abuse the pardon process—with an attempted self-pardon, or with a pardon of his son, or of his son-in-law, or of his attorney general. Theoretically, those pardons could undermine investigations and thwart prosecutions.

But they cannot prevent impeachment—or its consequences.

Indeed, a president who abuses the pardon power makes a case that reluctant Democrats and recalcitrant Republicans would be compelled to recognize. The impeachment power was developed for many reasons, but above all it exists as a tool for ending the corruption of the executive branch by lawless presidents.