WASHINGTON

As Donald Trump's campaign promises have been dunked in reality's strong solvent, many have been transformed in one way or another — modified, moderated, qualified, abandoned or pushed off into the distant future. Not a wall across the whole southern border. Not every part of Obamacare repealed. Not all illegal immigrants deported, at least in the foreseeable future. Not literally tearing up the Iran agreement. Not an actual prison cell for Hillary Clinton.

All this has opened up Trump to the charge of being a hypocrite. For the nation's sake, let's hope so.

Hypocrisy has always been a complicated vice. It is the easiest, most common charge made in politics ("My opponent claims to love apple pie but uses them regularly in unspeakable acts.") Most of us feel a visceral reaction when a crusading prosecutor makes use of prostitutes, or a law-and-order judge takes bribes, or a moralizing pastor tends to his or her flock a little too closely.

But we should take care in defining hypocrisy. "A hypocrite is a person who — but who isn't?" said Don Marquis. More helpfully, British political scientist David Runciman says that hypocrisy involves "claims to a consistency that one cannot sustain, claims to a loyalty that one does not possess, claims to an identity that one does not hold."

Hypocrisy comes in a long continuum of seriousness. You can wear a false face in displaying good manners toward someone you secretly despise. There is often hypocritical deception involved in political or diplomatic negotiations, which generally start with principled, nonnegotiable demands that are negotiated away in the process of finding a compromise. Hypocrisy can come in accommodating human realities that don't quite fit our ideals, as in the widespread use of artificial birth control by American Catholics. Or it may be that you have simply changed your mind in light of new circumstances — as President George H.W. Bush did in violating the pledge: "Read my lips; no new taxes."

In one sense, hypocrisy is unavoidable and necessary. If people were required, at all times, to live up to ideals of honesty, loyalty and compassion in order for those ideals to exist, there would be no ideals. Being a moral person is a struggle in which everyone repeatedly fails, becoming a hypocrite at each of those moments. A just and peaceful society depends on hypocrites who ultimately refuse to abandon the ideals they betray.

Before we become overly self-forgiving, it is worth recalling that the founder of Christianity took hypocrisy quite seriously: "Be careful not to practice your righteousness in front of others to be seen by them." Purity of heart and motivation, in the Christian tradition, does matter. But the hunt for hypocrisy should begin in the mirror.

The issue at hand, however, is a certain kind of political hypocrisy — the conscious use of a mask to fool the public and gain political benefit. Most would concede that this type of hypocrisy is generally harmful for a democracy, in which self-government requires informed choices. Trump's brand of personality-driven politics — emphasizing the virtues of a single leader — exaggerates the challenge. Trump arrives in Washington claiming to be the only honest man in a world of mendacity. It is a long way down from such a pedestal.

Some of Trump's strongest supporters seem to assume his cynicism. The part about forcing Mexicans to pay for the wall, according to Newt Gingrich, was "a great campaign device." Of the largest construction project since the Qin dynasty, Rush Limbaugh now says he never expected Trump to do it.

In this case, perhaps surprisingly, I am all for the wisdom of Gingrich and Limbaugh. Trump presents a special case, in which the normal criticisms of political hypocrisy should be suspended. Every time the Trump agenda is reshaped or refined to better fit reality, even Trump's most dedicated critics have reason to applaud.

This is a rare ethical circumstance in which realism and good sense take the form of hypocrisy. On a variety of issues, the sincerity of Trump's current intentions — or the cynicism of his past intentions — should not matter. If the candidate who gave a wink and nod toward white nationalism now repudiates the alt-right and promises to "bring this country together," so much the better. If the candidate who promised a trade war with China reconsiders, it is all to the good.

It is admittedly an odd thing to cheer for cynicism. But in this strange, new political era, hypocrisy is our best hope.

Michael Gerson's email address is michaelgerson@washpost.com.