In January of 1974, Gov. Marvin Mandel declared an end to the era of corruption in Maryland,

"Maryland," he told a grim session of the state legislature, "has become . . . a postmark for greed,for corruption, for kickbacks and payoffs . . . for a way of life that is less than honorable." Those days, he added emphatically, were over.

At the time he made the speech, however, Marvin Mandel was already accepting what would eventually amount to $350,000 worth of gifts, trips and bogus "legal fees" from four businessmen who were his friends.

It was the combination of these gifts and the influence he used to benefit the givers that led to his conviction in federal court Tuesday on charges that he used his office for for personal gain.

No matter what rhetoric there is for change, one observer said recently, nothing ever really changes in Maryland. "If these prosecutions have created anything," said former Anne Arundel County Executive Joseph Alton. "It's not a newsense of morality. It's just a new sense of fear and cautiousness.

This caution is born of a series of successful corruption prosecutions. In the eight years since Senator Daniel F. Brewster (DMd.) was indicted on bribery charges, there has been only one brief period - five months in 1975 - when no corruption charges were pending against a major Maryland politician.

Mandel's conviction makes hin the 14th elected official in Maryland to sucumb to a political corruption investigation in the last 13 years. And he will be the second Maryland governor in a row to be punished for violating federal laws; former Vice President Spiro T. Agnew was the first.

Throughout this succession of prosecutions all the defendants and their supporters have availed themselves of one unwavering argument: the standard of propriety to which they were held in the courtroom was far sterner than the prevailing standards of the world in which they had wheeled and dealed.

Allen Spector, a longtime Democratically of Mandel's whom the governor recently appointed to the judgeship on the Baltimore City District Court, repeated the old refrain shortly after he heard of the governor's conviction.

"It's like they changed the rules in the middle of the ball game," Spector said. "In politics, we were all raised with the idea that the guys who helped you, you favored."

And like all the disgraced politicians who came before him, Mandel insisted after his conviction that he has done no wrong. "I want to say to the public of this state that I have never during the tenure of my office ever defrauded the people or the public of this state of anything," he declared,

Nearly three years after Joseph Alton pleaded guilty to extortion charges and admitted steering who paid him kickbacks, he still feels the same way. "I never did one single thing in my public life that I then or today have any conscience about," he said recently.

Another Maryland politician, state Sen. John J. Bishop (R-Baltimore County), who has watched as the careers of a vice president, a senator, a congressman and two executives were shattered in the countroom offered this explanation:

"The basic mistake comes at the beginning, when, because he elected, the politician assumes he's in a different category of morality."

And Jonathan Goldstein, the U.S. attorney in New Jersey, whose office has won convictions against dozens of politicians, added that, "what really happens is that the people paying and the people taking the money beleive it's a legitimate transaction . . .

"They cosntruct a series of falsehoods, and they end up being convinced by them," Goldstein added.

For under the Maryland system - a system prosecutors say is by no means unique - a politician, upon election or appointment to government office, is eligible to become a broker in a busy world, trading influence, or contracts or government jobs for cash, or gifts or politicial contributions.

It all worked very smoothly until the federal prosecutors got into the act, applying the squeaky-clean tenets of federal law to the well-greased worlds of Baltimore and Anapolis.

"Some guys just can't believe that we'd want to put people in jail simply because they'd committed a crime," said Stephen H. Sachs, the U.S. attorney in Baltimore from 1967 to 1970. "They think the sun can't rise or set without the fix being in."

It was during the tenures of Sachs and his predecessor, Joseph Tydings, as federal prosecutors that corruption prosecutions started to dominate the Maryland scene. The first politician toppled was the Speaker of the House of Delegates, A. Gordon Boone, in 1964.

Boone was convicted of mail fraud - the same charge that Mandel was - found guilty of - after the collapse of the savings and loan company he has invested in had lobbied and legislated for.

Then came the influencepeddling scheme that in 1968 brought down Rep. Thomas F. Johnson from the Eastern Shore.Then there was the extortion trial of Baltimore County State's Attorney Samuel Green, a trial that degenerated into longwinded descriptions of the defendant's sexual excapade

And then there was Spiro T. Agnew.

One dramatic day in October, 1972, Agnew resigned the vice presidency of the United States and pleaded no contest to a federal charge of felonious tax evasion stemming from an investigation of kickbacks he allegedly had accepted.

By the time he had left the federal courthouse in Baltimore after his plea. Agnew had pushed Maryland to the foreground of the nation's heirarchy of corruption. Like New Jersey and Illinois before it, Maryland, as Mandel said, had become "a household world . . . for corruption."

The investigations into allegations of corruption continue.

Just three weeks before Mandel's conviction, former U.S. Democratic Rep. Edward A. Garmatz was indicted for allegedly selling his influence when he was chairman of the House Merchant Marine and Fisheries Committee.

But it's not that Maryland is unique in any of this, Alton and other observers contend. It's just that in Maryland - like New Jersey of Illinois - the politicians get caught.

"The difference between Maryland and other places is Mr. Skolnik," said Alton, referring to Assistant U.S. attorney Barnet D. Skoinik the driving force in every political corruption prosecution since Congressman Johnson's.

"If you put that man in another state," Alton added, "he'd do exactly the something." There was an overtone of admiration in his voice, an obvious respect for the man who forced him out of office and into prison. "I've never seen a man with such drive."

There are those, though, whose admiration for Skolnis's mastery of his work is tinged with contempt. "Barney thinks that everyone in the world is corrupt except him," said one former aide to a politician whom Skolnik forced into court.

Beneath the disparaging words was the unspoken thought that Skolnik's laws and ethics are suited only to choirboys and have no place in a workaday world.

The politicians whom Skolnik has brought down hardly consider themselves without ethics. They live by their own code, an unwritten law that has far more meaning to them than the niceties of federal statutes.

Culled from the sayings of politicians, this Maryland morality has a few basic tenets. Loyalty is the paramount virtue. Stealing from the treasury - taking money from the taxpayer - is a sin, but taking anonymous cashstuffed envelopes from contractors is not.

Overt greed, like that shown by Alford (Skip) Carey - who was convicted in 1976 of embezzling $22,105 from the state school constructioin program he headed - is not condoned. Neither is squealing - testifying against a colleague in the tightly woven society of politicians and businessmen.

"I don't think I'd have had any problem getting out of my trouble if I'd squealed on someone else," Alton says, quietly proud that he never succumbed to this templation.

For years, state Sen. Bishop was shunned by his colleagues, after he helped tape his conversations with another politician who tried to buy Bishop's vote. Bishop's tapes and testimony later helped send Thomas Raimondi, who had run for Congress unsuccessfully, to jail.

Raimondi was later pardoned by Gov. Marvin Mandel.

In another, more recent, hiddentapes case, the jury and spectators in the extortion trial of former state Del. George Santoni (D Baltimore) were given an instant education in Maryland ethics.

At one point, the legislator was recorded telling another, politician: "You can question my work, you can question my honesty, you can question my integrity. But don't you ever questioin my loyalty to you."

The voters who live in these politicians' neighborhoods and have re-elected them again and again over the years seem to accept the code as a fact of life.

"Marvin Mandel never broke any laws that mean anything to you or me," Cecil County real estate speculator Harold Montgomery said recently when he was asked about a $10,000 loan of his money that had been funneled though a Mandel aide to the governor.

And even the voters of Baltimore County, who elected as County Executive a thenpolitical unknown named Theodore Venetoulis after he ran on a reform platform, remain cynical.

From 1962 to 1975 the county was run by two county executives - Spiro Agnew and Dale Anderson - who were later punished by the courts for their parts in the illegal everyday business of the county.

Even now, "when people are talking to me honestly," said Venetoulis aide Jackie Smelkinson, "they say that they have just as many doubts about the honesty of this administration as the others."

A prosecutor like Jonathan Goldstien shares that generalized distrust of politicians, and not just in Maryland or New Jersey or Illinois. For eight years, he has served in the U.S. Attorney's Office in Newark, inheriting and continuing the corruption fighting tradition of his rpedesesors, former U.S. attorneys Herbert Stern and Frederick Lacey.

But behind all the illegalities, he contends,is "greed. Pure greed." The corrupt politician, he said, "feels he's entitled . . . to drive big cars pick up the tab in expensive restaurants and have his wife or girl friend decked out in furs.

"They feel entitled to it - so they go and get it any way they can."

It wasn't hard to find readily available cash in the fastgrowing Maryland suburbs of the '30s and '60s. People wanted houses away the city, with their own patch of lawn to tend. Developers wanted favorable zoning decisions, so they could build houses and make money.

Then, the growing communities needed roads and bridges and better and bigger government buildings, It was up to the elected officials to find the architects and engineers to design and build them.

"It was simply a convergence of needs," explained Bishop.The politicians needed money - for their campaigns or for themselves - and the contracters needed government rulings.

Most observers agree that the system is a little more surreptitious now, however. And now that the era filled with contracts and questionable cash has receded somewhat before the prosecutors onslaught, there is strange residue of nostalgia.

It shows, sometimes, when the people who have knows the politicians gather in an office or a restaurant and start to remember how the white envelop flowed in to officials in return for this bridge or that road. For them, the Maryland landscape is dotted with steel and concrete monuments to the payoffs of the past.

"You see that car dealershop sign?" one businessman with close politicalties asked me one recent gathering. "That was one politicians first payoff." He smiles at the memory of the price it took to bend a zoning rule on roadside signs 15 years before. The businessman didn't believe that any of this had stopped. Like Alton, he believes that the system is too firmly entrenched in Maryland politics to ever really go away.

Goldsten, from his vantage point in New Jersey, feels the same way. "You're not really going to be able to stop this," he said. "You've got to try to control it. But I'll be the first of tell you're not going to stop it."