One way you can tell a Republican from a Democrat in this era of blurred distinctions is that Republicans are emotional about the interiors of their superiors. Once they have elected a person to high office, they are passionately concerned that the decor provided by public funds may be insufficiently elegant.

The thought of a rent in the Aubusson, a chip in the Chippendale, a gap on the china shelves has the effect on the Republican that a picture of a starving child in east Africa produces in your average bleeding-heart Democrat. Misty-eyed, he writes a check.

The response of the haves to the Reagans' refurbishing needs was phenomenal. Mrs. Reagan turned down the $50,000 provided in the federal budget and announced a drive for public donations. Within six weeks, stricken friends had contributed $822,640, and the fund had to be closed before beauty-mad oilmen sent it to the level of their company profits.

The president's oft-proclaimed faith in the princeliness of merchant princes was amply fortified, and among his own, at least, the response furthered his notion that the private sector could be counted on in aesthetic emergency.

Having rescued the executive mansion from any threat of tackiness, the Reagan Republicans set about fixing up the vice president's house with private donations, which only friends were allowed to make--this is compassion of the rich, by the rich, for the rich.

A rationale for conspicuous consumption has been offered by Charles Wick, who as the head of the International Communications Agency interprets us to the world. He explained that the tableau vivant of opulence provided by the Reaganites is dynamite at the box office of public opinion, that Americans love the spectacle, just as they lapped up lavish movies during the Depression.

It could be. Reagan is holding up well in the polls. But there may be a tiny difference. Franklin D. Roosevelt wasn't telling kindergarten children to tighten their belts. Ronald Reagan has just decreed that preschoolers will have their daily milk ration reduced from six ounces to four.

Other Republicans truly believe that they are inspiring the masses by giving them these glimpses of life at the top. They will work harder, save more if they see the diamonds glittering at the end of the tunnel.

On the other hand, the Republicans may just be applying the famous dictum of F. Scott Fitzgerald's friend who said, "The best revenge is living well."

After 40 years of being taxed white for the ungrateful poor, of being expected to worry about people they didn't even know and surely would never meet at the country club, they are free, free at last from the loathsome hypocrisies of the "respectable Republican cloth coat" of Richard Nixon and the populist blue-jeanery of Jimmy Carter. Many of them believe that last November was a mandate for the black mink and the long limo.

But parody lurks like a mugger around these revels, and last week parody struck. Just as the Department of Health and Human Services was announcing new austerities in the standards governing eligibility, the secretary of the department, Richard S. Schweiker, appeared on the cover of The Washington Dossier in white tie and tails seated at a banquet table amid the baronial splendors of the Columbia Historical Society.

Beside him stood his wife, arrayed in crimson taffeta with sleeves puffed to dirigible fullness, white gloves that appeared shoulder-high and a gold choker.

Now, of course, it is possible that the ghetto dweller who has just lost the CETA job, the 80-year-old widow whose minimum Social Security benefits are about to be cut, and the schoolchild who is going to get a smaller hamburger on his federally subsidized lunch plate will all rejoice to see that the secretary is having such a swell time and is not so worried about them that he cannot sit down to practice for a five-course banquet in advance of a Victorian ball that will be held next month.

The secretary may console himself that his clientele does not read Dossier and that Ronald Reagan, whose friends' pictures dot its pages, does and will be pleased to see that Schweiker, a liberal in another life, has become a team player in the opulence game.

The trick, if pikes are not to be raised outside the White House gates, would be to steer Republican interest and largess to exteriors. Let Frank Sinatra and Armand Hammer and Walter Annenberg get interested in doing up the South Bronx or smartening up the riot corridor in Washington. The difficulty is that these are places they never go and sincerely hope they will never be invited to. What they don't see doesn't hurt them and their friend Ronald Reagan. That's plainly what they think anyway.