Pity poor battered Detroit, the crusty, old millhand of American cities, so often maligned, ignored and imposed upon.

This year he was finally going to mingle with the country club set. City fathers persuaded the Republican Party that the old guy had developed class, and the GOP agreed to bring its entire national nominating convention to meet him.

It would be a symbol of the party's new-found interest in urban America, said the Republicans. It would be a symbol of the city's renaissance. "The entire world will see the Detroit which once was declared dead is indeed alive and well," said Mayor Coleman Young, a Democrat.

But when the GOP delegates and the network television crews arrive here in July, they will find a city in the depths of one of the deepest recessions since World War II, a city whose key industry -- auto manufacturing -- is facing cardiac arrest.

The numbers that the computers are coughing up about Detroit and the rest of Michigan these days are devastating. So are the forecasts from the economists:

Unemployment is 15 percent in the city and rising. More than one of every four auto workers has been laid off. Black unemployment is about 25 percent, and the state employment security commission estimates it may reach 55 percent among black teenagers by summer.

Statewide, more people are on welfare than any time in history. In Detroit, one family in four receives some sort of public assistance.

The city of Detroit is in such bad financial shape that Young is laying off 703 police and 40 fire fighters this year, reducing the city fire department to its smallest size since the 1920s. To make matters worse the city's contract with police expires on July 1, less than two weeks before the Republican convention, and the Detroit Police Officers Association has threatened to strike.

The city school superintendent, facing a $28 million deficit, has proposed firing 600 of Detroit's 12,000 teachers.

Inflation, running at a 14.8 percent annual rate, is eating into pocketbooks. Last year the typical Michigan factory worker made $375.74 a week or $177 in 1967 dollars. Today he gets $375.38, or about $154 in 1967 dollars.

Instead of a symbol of urban rebirth Detroit may become a symbol of a nation on hard times and of the Carter administration's failed economic policies -- an embarrassing symbol for Coleman Young, one of the president's staunchest black supporters and chairman of the Democratic Party's platform committee.

Republicans regard it as a mixed blessing, a lemon to be turned into lemonade. The drumbeats of summer can already be heard. "Jimmy Carter's economic policies have been devastating in terms of what has happened to this area," GOP presidential contender George Bush said here the other day. "It's not an exaggeration to say that as Detroit and Michigan go, so goes the nation."

Detroit's corporate power structure obviously would like things to be different, realizing that its dream of a flood of favorable publicity because of the convention may turn to dust. But it, too, is trying to make the best of a bad situation.

"The city has really turned around," said William Agee, chairman of Bendix Corp. "All this will do is put the focus on a very serious problem -- the auto industry. I look at this as an opportunity, not a problem. It will raise the consciousness of what's wrong with the country."

Detroit, the Motor City of the world, has always meant cars -- big cars, gas guzzlers that have become dinosaurs in this energy-crunch age. Today they are parked, unsold, on lots all over the city.

And despite the fact that auto workers here enjoy some of the most liberal unemployment benefits in the country (many take home 90 percent of their wages when laid off) people are uneasy about their futures.

Listen, for a moment, to a few of them.

Walter Bradley was laid off after 16 years on the Chrysler assembly line:

"I think most foreign-made cars are better than what we make. You don't see any Japanese cars alongside the road broken down. They make them to last.

"If they don't sell no cars, this town is going to be like a ghost town in six months. I don't see the town bouncing back for two or three years. There's not going to be a job market."

Bob Freeman is the father of four and out of work.

"It's getting rough out there and it's going to get rougher. I was laid off in '75 for a few months and things seemed bad. But inflation has made things a lot worse.

"My plant is still open, but I only had 12 years of seniority so I got bumped. I don't know if I'll ever get called back. I'll take my 26 weeks of benefits, then think about relocating."

Javier Sanchez came to Detroit 16 years ago from Mexico seeking the good life. He was still working, but this day Chrysler had put up a notice that the Lynch Road plant where he worked 16 years was going to shut down:

"You feel bad. It means I've given up half my life. It's going to be hard to come back. The auto industry is dead. It's like a dying man. It's like a sickness has taken over.

"I blame it on the auto executives not looking ahead. They didn't supply what the people wanted. They tried to stick with the big cars. Nobody wants a gas guzzler when gas is selling for $1.40 a gallon.

One more voice is helpful here. It belongs to Bill Snethkamp, whose family has owned a Detroit Chrysler dealership since 1926. He thinks his dealership will survive, if only because his three competitors in the inner city went broke this year and closed down.

"We didn't even know there was a recession when things were supposed to be so bad in 1975," he said. "I don't think most dealers did. We've survived up to this point. But it's been dropping."

Strangely enough, there is a note of genuine optimism in almost every voice one hears from Detroit this spring, optimism about the city, not the economy.

Everyone realizes that Detroit is on hard times. But it has been on hard times before. Much of the hopelessness that so permeated the city a few years ago is gone.

Almost everyone insists Detroit is a better, safer place to live than a few years ago when it was known as Murder City, U.S.A. There is an unmistakable sense of marvel about the trees being planted in parks, pride about being selected as a convention site, potholes being filled in expressways, and storefronts remodeled for the first time in a generation.

But what tensions exist appear to be about the fact that Detroit, like its cars, may be going into a period of "downsizing," rather than any immediate serious trouble.

Joe Richmond, a laid-off auto worker and father of two, put it this way:

"Coleman Young has done a lot for this city. Crime is down. Buildings are going up. The police force is a lot better. They're tearing down abandoned buildings. They're trying to make the education system work. Everything is better.A lot of people used to be afraid to come to Detroit. Everyone said it was the drug and murder capital. Now it isn't like that."

Max Fisher, multimillionaire and cochairman of the Detroit host committee, said the image of Detroit as a city on the rise is still true. "This is a temporary phase," he said. "Detroit is going to be here. It isn't going to go away. General Motors is going to be here when you and I are dead and gone. And it's going to be making cars." b

There is little doubt that Detroit has turned the corner on some of its most obvious problems. Its homicide rate, for example, dropped from 714 murders in 1974 to 416 in 1979. Middle-class whites are moving back into the city, and a visitor senses a new vitality downtown. People are coming downtown to eat in restaurants -- some in an old warehouse district known as the home of "the gritty chic" -- and visit its glistening Renaissance Center.

But serious problems remain.One of these was brought home to Mayor Young last winter when a police precinct commander and seven other officers were charged with strip-searching the mayor's niece and two of his sisters in a dispute over a parking space.

A Detroit News reporter found a problem of more immediate concern to convention delegates on a sign in the rooms of a downtown hotel. "All locks changed weekly for your protection," it advised.