“History furnishes one example only of a first Magistrate being formally brought to public Justice. Every body cried out against this as unconstitutional. What was the practice before this in cases where the chief Magistrate rendered himself obnoxious? Why recourse was had to assassination in which he was not only deprived of his life but of the opportunity of vindicating his character. It would be the best way therefore to provide in the Constitution for the regular punishment of the Executive when his misconduct should deserve it, and for his honorable acquittal when he should be unjustly accused.”—Benjamin Franklin at the Federal Convention, 1787

Most of the delegates to the Constitutional Convention did not want to include any mechanism at all for impeaching a president. Their primary model for a chief executive was the British King, who was, by definition, above the law.

For most Enlightenment theorists, this was an element of pragmatic statecraft. Succession crises were dangerous to a nation, and a stable executive—even an obnoxious one—was better than a power vacuum.

But Benjamin Franklin played dirty. He reminded them of the most chaotic period in England’s recent history—the 1649 execution of Charles I, which originally created the protectorate of Oliver Cromwell, but which led to serious succession crises in 1660, 1688, and 1714.

The instability created by Charles’s execution was so great, Franklin argued, because there was no Constitutional provision for removing a chief executive without killing him.

Impeachment of the President, and other high-ranking officials, was included into the Constitution because Franklin convinced the delegates that the safety of the state required that there be a way to remove executives without killing them. The bar for removal was intentionally set very high — 50 percent of the House of Representatives and two-thirds of the Senate — to ensure that it did not become a routine way for the legislature to apply political pressure.

All of the delegates saw that as unacceptable. Impeachment was originally seen as an alternative to assassination; it was supposed to be really, really serious.

This has largely been the way that Congress has used the impeachment process. When Jefferson tried to use the impeachment process to remove a Supreme Court Justice whose opinions he disagreed with, his own party recognized the Constitutional danger of such an approach and refused to go along with the plan.

As William Rehnquist has written, the impeachment trial of Samuel Chase was a watershed moment in Constitutional history, as it established for all time that a federal judge could not be impeached for making judgments.

Much the same has been true of executive trials.

Only eight federal officials have ever been removed through impeachment, all for clearly illegal behavior that had nothing to do with their conduct of their official duties. The trials of the two presidents who have been impeached — Andrew Johnson and Bill Clinton — did not end in removal because the prosecutors could not overcome the political barriers put in place to make overturning elections very difficult.

Threatening impeachment, however, has become a distressingly common political trick.

Every president of my lifetime (which began during LBJ’s second term) has been threatened with impeachment by legislators of the opposing party. It has actually come up with Obama less than it did with Reagan during Iran Contra or Bush II during the Iraq War.

Anyone who has listened to our legislators talk during the last 30 years would swear that impeachment was a regular part of American politics.

Even by these inflated rhetorical standards, however, Senator Ted Cruz’s

declaration last week — that Eric Holder must appoint a special prosecutor in the IRS affair or expect to face impeachment — should give us pause.

Cruz is invoking the threat of impeachment as a political tool to force the Attorney General to invoke a law that was designed to place criminal investigation beyond the reach of political pressure. That is ironic. But he is also implicitly arguing that impeachment is acceptable when a member of the executive branch fails to perform an executive function to the satisfaction of the legislature.

This is a flat misunderstanding of a Constitutional process.

Yes, I know that Cruz is merely posturing to an element of his base that sees impeachment the way that a hungry lion sees a big raw steak. I know that he has no intention of bringing impeachment proceedings against Holder. And I suspect that he even knows that such proceedings don’t even originate in the legislative body of which he is a member.

I recognize demagoguery when it slaps me in the face.

However, when a legislator says, “if you don’t do X, you will be impeached,” he or she turns a serious Constitutional process of last resort into a tool of routine political pressure -- thus threatening to create a Constitutional crisis simply to score political points. This is something that should concern in any case, but perhaps especially if the legislator in question regularly talks about respecting the Constitution as though such were a good thing to do.