The day will come when Marion Barry will be spoken of in the past tense.

That reality, of course, applies to all of us. But Barry’s vincibility is especially useful to note because of his penchant for bringing shame on himself and the city.

In the latest line-crossing of his career, Barry managed to draw fire this week for remarks he made about “immigrants . . . particularly from the Philippines” taking nursing jobs in the United States. The Philippines’ ambassador to this country, Jose L. Cuisia, issued a statement denouncing Barry’s remarks as “intolerant and narrow-minded.”

Not a month earlier, Barry went off about “Asians coming in, opening up businesses, those dirty shops.” He later said his remarks were taken out of context and that he could have phrased his remarks differently, but that his point still stood. He then grudgingly apologized. Barry, I suspect, is now about done with Asia.

There is, however, a big world out there. With six other continents potentially at his disposal, there is plenty of geography on which Barry can try to lay blame for all the ills befalling his Ward 8 constituents.

Diplomatic corps, en garde.

After 40 years of observing him and more than 20 years of writing about him, I no longer feel my jaw drop at anything that comes out of Marion Barry’s mouth.

When it comes to Barry, a moment’s thought is a moment wasted. But he does have moments of cold calculation.

I have also learned that there can be a method to his madness.

He didn’t become the most dominant figure in D.C. politics by accident, although his power has now been diluted to next to nothing.

That’s because the District of the 21st century is, demographically, culturally and politically, not the city that Barry once was able to play like a harp. Ward 8, the city’s most impoverished district, which Barry has represented since 2005, is now the outer limits of his influence.

So long as he remains with us, it might be useful to understand what Barry was once upon a time, and still is in his autumn years.

In his heyday as mayor of “Chocolate City,” Barry was the characteristic old-style black politician in the mold of the late Adam Clayton Powell.

Noted African American psychologist Kenneth Clark devoted much of his 1965 book, “Dark Ghetto,” to Powell, but he could have been describing Barry.

Among the things Clark wrote: “He uses his appeal without apology.” Powell had to be understood, he said, in terms of the massive pathology in the community he represented. It’s “where a powerless people seek a concrete hero who will fight the battles they cannot fight for themselves.” “All the better,” wrote Clark, “if the hero defies and taunts the white enemy. Here is the gratifying joy of vicarious revenge without the attendant penalties of a real encounter.”

Clark astutely observed that “in his flamboyant personal behavior, Powell has been to Negroes a symbol of all that life has denied them.”

As for personal conduct, Clark explained: “The Negro masses do not see Powell as amoral but as defiantly honest in his protest against the myths and hypocrisies of racism. What whites regard as Powell’s violation of elemental ethics, Negroes view as effective and amusing defiance. Whatever the personal ethical and moral standard of the individual Negro, it tends to be suspended in judgment of Powell. He is important precisely because he is a caricature, a burlesque, of the personal exploitation of power.” Barry, anyone?

Clark also wrote of Powell: “He seems a simple hedonist above all else. He appears free of any sense of guilt. Guilt is the consequence of a sense that one has violated what one believes in, a consequence of behavior in conflict with one’s conscience. To be rid of such conflict is to be free of much anguish.”

Hence, our worry-free Marion Barry, unencumbered by principle.

Powell, like Barry here in Washington, was frequently criticized in newspaper editorials. But those editorials only strengthened Powell in New York’s black community — much as criticism of Barry once raised his appeal among some District residents.

Observed Clark, “When Powell is condemned by respectable whites, this is taken merely as evidence of his effectiveness, for clearly whites would not be concerned with an impotent Negro!”

Powell understood that, Clark noted, and used that knowledge to maintain power.

So, too, did Barry, who, to this day, remains unchanged.

The difference? The District has changed on him.

To say the city has risen above the constrictions of race would be a lie. But Washington, D.C., is now a different place. And it will outlive Marion Barry.