Marvin Mandel appeared on the steps of the federal courthouse at 3:15 this afternoon and did what he has done so many times during an ordeal that has found him tried, convicted and now sentenced to prison on political corruption charges.

He told the press and the public, that he did not regret his actions. He said it calmly, almost proudly, and he made it clear that he was not about to show any deeper emotions.

The man who prosecuted him, Barnet D. Skolnik, had charged earlier in the day that the ex-governor of Maryland was callous, that he was unable and unwilling to express remorse for his illegal deeds. Mandel said that was not the point.

"How do you show remorse?" he asked reporters, a sly smile moving into shape. "Do you go around crying? I've never been one to go around crying."

Almost everything Mandel had to say was in this imperturbable style. He said he found "no quarrel" with the four-year prison sentence imposed by judge Robert L. Taylor. He admitted to a feeling of "satisfaction" with his 25-year career in politics. He said he started with nothing and was back to nothing, at least in financial terms. Then he shurgged. It was his most expressive gesture.

But Mandel was the only principal figure at the courthouse today who made it seem as though this was just another day. The others offered moments of drama high and low. There was Skolnik trundling into the courtroom sporting a villainous moustache. There was defendant Irvin Kovens shouting that he was not and had never been a political boss. And there was defendant Ernest M. Cooy, stoop-shouldered and hesitant, telling the court that he carried "a heart full of remorse and contrition."

The sentencing began with Judge Taylor expressing a remorse of his own. "The governor's case has given me as much or more concern as any case I've ever tried," he said. "It's troubled me, troubled me. You don't know how much it's troubled me. I think about him losing his governorship. I think about him as a struggling lawyer. I can't tell you in words how much I'm troubled by this case."

Mandel's attorney, Arnold M. Weiner, attempted to put his thoughts into a few hundred, or thousand, words, replete with phrases such as "These proceedings in and of themselves have worked an incredible punishment (on Mandel" and "When the (prison) door slams behind him, the whole man is left inside."

At about the time when Weiner was reaching a melodramatic peak, however, Judge Taylor interrupted to ask Weiner just how much money Mandel paid him in legal fees. Weiner, redfaced, told the judge he would reveal the entire fee in chambers and would say publicly only that Mandel still owed him $190,000.

"You men here in Baltimore charge that much" responded the country jurist from Knoxville, Tenn. The query drew applause and laughter, as Taylor knew it would.

Weiner ended his remarks by noting that prosecutors sometimes ask the court to impose lenient sentences. This was too much for Skolnik to take without comment.

"Where we think it appropriate, we do in some instances make clear our views that are favorable toward leniency for some defendants," the prosecutor said crisply. "Mr. Weiner does not represent one of those defendants."

Of the other defendants, only Kovens seemed out of character during the sentencing. W. Dale Hess and Harry W. Rodgers were relaxed (William Hundley, Hess' lawyer, went so far as to say that his client gave the trial "a tremendous show of class"); William Rodgers was polite; Ernest-Cory was humble.

But Kovens, the man who has been called Marvin Mandel's political godfather, the silver-haired millionaire who rarely loses his sense of place, was angry and at times vicious on this day.

At the end of the proceedings, with his two daughters exploding with tears, Kovens walked over to Skolnik's table and confronted the prosecutor and his boss, U.S. Attorney Jervis Finney, with an unsubstantiated charge that Skolnik's sealed divorce papers reval some "tax irregularities."