David Marston: bright, eager, ambitious, young unemployed.

"I don't want to be a John Dean. I'm not going on lecture tours. As soon as you start to profit out of something like this, people start to wonder."

Are you going to be on "A.M. America?"

"On Friday."

Marston, 35, former U.S. attorney in Philadelphia was, by his own account, spectacularly fired - "Fired on national TV by the attorney general and fired again in the attorney general's office" - He launched himself as a private citizen yesterday - speaking before the National Press Club.

Unknown outside Philadelphia a few months ago. Marston is now trailed by network TV cameras and photographers, the William Morris Talent Agency can't get him to return their calls. He installed a second line on his phone in his Philadelphia town house for press inquiries and sympathetic calls from strangers - "at least a dozen of whom cried," he recounts.

He generates some of the most obvious alliteration: the Marston Muddle, Marston Mess, Marston Massacre. Another could be "Marston: media Martyr."

And he generates as much public response as Bert Lance. By White House count, 9.629 telegrams, letters and phone calls urged the retention of Marston before his ouster. Five citizens wrote in favor of firing him. After his dismissal last Friday, the White House received 3,972 telegrams and letters protesting his firing. And none in favor of the administration's action.

The fact that he is adroit at selling himself and his message is an embarrassment to the administration, a delight to the Republicans, grist for reporters and makes him a folk hero to many Pennsylvanians.

"About 60 of them (U.S. attorneys) have been replaced with very little noise," grumbles Marvin Wall, director of public information for the Justice Department. "It's been very profitable for him, he's going to play up the political angle."

The main difference, however, between Marston and the 60 (out of 94) other replaced U.S. attorneys is that this time, a congressman, Rep. Joshua Eilberg, reportedly under investigation by Marston, called the president urging Marston's ouster. The president says he knew nothing of the investigation, but did contact the attorney general after Eilberg's call.

A dozen cameramen and photographers loomed in front of Marston Wednesday, blocking the view of some in the packed house - the regulars who turn up just because the luncheons are there, mingling with working press. Marston, who has a tendency to slouch, gripped the lectern and moved into the Eilberg phone call, a subject he dramatizes wherever he goes.

"When the president plays poker with Congress, I don't think the U.S. attorney's offices should be one of the bargaining chips. If a single congressman can remove his hometown prosecutor, who is actively investigating public officials, with a single phone call to the president - and that's what did happen - our federal justice system can't and won't work."

Justice Department spokesmen say Marston is wrong; that he was marked for extinction months ago; the Pennsylvania Democrats just could not agree on who should be his successor.

Congratulating Marston on his speech were Sen. John Heinz and Marston's former boss, Sen. Richard Schweicker.

He was asked the cruical question: Who knew what when about Eilberg and allegations that focus on legal fees his law firm received from a Philadelphia hospital. Marston employed a perfect out. It would not be proper to speculate on an on-going investigation, he said. He did reiterate that he told key Justice Department official Russell T. Baker about the investigation last November and Baker told Criminal Division chief Benjamin Civiletti.

There are apparent conflicts between these two about what happened next, Marston noted, throwing the ball neatly back to Justice. "And that's where the matter sits." Both Heinz and Schweicker said it would all be pursued at upcoming confirmation hearings for Baker (U.S. attorney-designate for Maryland) and Civiletti (designated deputy attorney general). Schweicker thought it highly possible Marston would be called on to testify at the hearings.

At the head table was New York Times columnist William Safire, former Nixon aide who has been championing Marston at every chance. Safire had to introduce himself to Marston who did not recognize him.

Marston is lean, with a prominent nose and receding chin. He fits the mold of many government lawyers - working 12-hour days, intense, serious. "We have almost no social life," he says of himself and his wife, Linda. To relax, he fishes with his family (Karen, 9, David Jr., 8, and Michael, 5) and reads John LeCarre novels.

Marston was born in Knoxville, Tenn., and his family moved to a Philadelphia suburb when he was 3. His father edited a trade journal of a chemical company.

Their 200-year-old townhouse on the fringe of Philadelphia's fashionable Society Hill was dramatically renovated by the Marstons, with skylights and exposed brick. The day before he was ousted the children talked easily to strangers about their father. "If President Carter fires him, he's dumb," said David Jr. Linda took the children out of school to watch the president's press conference. "We thought it might be important to our lives," she said. "I am disappointed, but David's tough and we'll survive."

Although Marston cannot recall any "deep, committed reason for going into law," his job was clearly an obsession. "He worked at home all the time. I was the victim of many an 11:30 p.m. phone call," recalled one aide.

Marston graduated from Harvard law and was an ensign in the Navy for two years - prosecuting drug busts on board ship - and worked in a Philadelphia law firm for four years.

In 1972 he ran for the state house and lost. A month later a state senator died and he ran in a special election and lost. "Schweicker heard about me at that time and asked me to joint his staff." After two years as legislative assistant, Marston asked Schweicker to recommend him for U.S. attorney in 1975.

Marston has been criticized for being a product of the patronage system and for not having prosecuting experience. "One of the best attorney generals this country ever had was Robert Kennedy and he never tried a case in his life," he says in defense.

As U.S. Attorney, Marston successfully prosecuted high Republican and Democratic politicians - including three major cases - in a state he calls "one of the most corrupt in this country." Critics say he was merely a clever administrator who hired and retained the best trial lawyers, regardless of party affiliation, but took the credit for their hard work.

Chief Judge Joseph Lord, a Democrat, said some of Marston's most celebrated cases were "ripe for picking." "One area he move in one his own was police brutality, and there he hasn't gotten a conviction. He did not do one stick of investigation himself, ran that office for his personal aggrandisement - and turned it into a TV studio.Assistants complained they couldn't walk around the office without tripping over camera cords."

Two former staff members interviewed and many of the press who followed Marston's career disagreed. "He was an outstanding leader and very courageous," said Gilbert Scutti, who was an assistant attorney before Marston arrived. "I'm now leaving a place I love because I'm convinced there is no justice in the Justice Department. Two months after Marston took office, he started an investigation that freed an innocent man who was convicted of murder and convicted the criminals. He didn't have to go after that.

In his office the day before his firing. Marston gulped orange and grape fruit juice, took calls from the press, sat for color portrait photos for a New York magazine. He talked about how the uncertainty of his future was crippling investigations: the "street people wouldn't talk any more."

Philadelphia observers said the national press was missing one major point which accounted for the public outery concerning Marston. In a state controlled by machines. Democratic and Republican, Marston was the last of many prosecutors to be ousted.

Marston himself constantly mentioned that Henry J. (Buddy) Cianfrani, while he was the most powerful member of the state senate, successfully cut off funds for two special prosecutors. "Buddy used to boast. "The guy couldn't be so special if he couldn't get anything on me.'"

In December, Cianfrani pleaded guilty to 106 counts on various charges - including obstruction of justice, tax evasion and mail fraud.

"Cianfrani's whole defense strategy was to get rid of me; it was in the court record. Cianfrani told his former mistress. "Get sick for a week, take some drugs and we'll get Marston thrown out. That was the whole strategy. So a week after that, word came that I was going to be thrown out." Marston was referring to newspaper accounts of a "secret" Justice Department meeting to oust him a few days before the president's explosive press conference.

Last Friday Marston slogged through snow that had derailed Amtrak, stopped planes and tied up the East Coast, arriving by Greyhound several hours late for his meeting with Attorney General Griffin Bell.

Pleasantries were few. No coffee was offered. Marston asked to stay on a full term. Bell said no. Bell asked Marston to stay on until they found a replacement.Marston said no.

Later in their conversation Bell remarked. "I can't seem to get through to you that you're a Republican and we're Democrats."

And like two well-schooled Philadelphia lawyers jousting, Marston and Bell debated the terms on which Marston might have been retained.

Marston pointed to Carter's campaign promise and Griffin Bell's comfirmation talk. "I believed Bell would retain those who were acting effectively and in a nonpartisan manner." But Marston left out an important word, in the game of politics. Bell actually said. "If there is a United States attorney who warrants retention on the merit system we would certainly give thought to retaining them."

Many are now speculating that Marston will turn the Marston Affair into a political plus. He is rumored to be a candidate for everything: lieutenant governor, governor. Philadelphia may or next year. The joke is that he'll run against Eilberg.

Cracking an infrequent joke, Marston said. "The only thing I'm running for is for cover."

Everyone laughted. But not everyone believed him.