Brimming with promises, Maryland's lawmakers returned here today for the 1978 session of the General Assembly, ready to begin the delicate job of balancing their legislative responsibilities and their political ambitions in this election year.

There was little talk of recent scandals on this largely ceremonial opening day, little talk of suspended Gov. Marvin Mandel, who was absent from the proceedings for the first time in more than 25 years.

Instead, the returning legislators exchanged effusive greetings in the marble lobbies of the statehouse, joshed with each other in the House chamber, mugged for ubiquitous photographers - then soberly pledged to do their best for the citizens of the state of Maryland.

There was also some serious business conducted on this brief working day, as the Senate overrode Mandel's 1977 veto of legislation increasing some state welfare payments, and both houses routinely re-elected their legislative leaders.

If there was any sort of tone to today's generally routine proceedings, it was set by a young Baptist preacher who opened the Senate session by praising democracy, praying that the lawmakers would act with strength and wisdom, and asking forgiveness for their foibles.

"Lord, you know the temptations are great for these lawmakers," intoned Howard Roberts from the Senate rostrum ". . . Protect them from the pressures of special interest groups. Do not let the serpent of personal advancement blind their wisdom and insight."

Looking out over the bowed heads of the Assembly, Roberts solemnly added, "Keep these lawmakers from making decisions solely on the basis of what will bring them the most votes on election day."

This tone did not change when, a few minutes later, Senate President Steny H. Hoyer moved behind the rostrum and took the place of Roberts, who is the minister pastor at Hoyer's own church in Temple Hills.

"In this election year, it will be even more difficult for each of us to be senators who can shun the politics of the moment of respond to the needs of the state," said Hoyer, who is a candidate for the Democratic gubernatorial nomination this year.

"This task will be difficult, but there is no reason to avoid it," Hoyer added. Then, briefly, he went through the ritual mohens of setting out the legislative package that he and the legislative policy committee will be hoping to enact this year - a package that includes measures to reduce property taxes for many residents by extending the "circuit-breaker" program that currently offers property tax relief for the elderly and the disabled.

But there were sharp departures from the past in this first opening day under the regime of acting Gov. Blair Lee. Whereas Mandel dispatched his controversial lobbying team to protect this vetoes, there was no evidence of Lee lobbyists. Some lawmakers were unclear about Lee's position on the veto issue.

"We didn't know what Lee wanted," said Sen. Victor L. Crawford (D-Montgomery). "I didn't get a message, an arm twist, I didn't even get a yank on my chain. In a way I sort of miss Mandel's Mafia (lobbyists) running around buzzing in everyone's ear. It's part of a bygone era."

Except when they were asked by reporters, few lawmakers mentioned the name of Mandel, a legendary political figure in these ornate halls, who had worked his will on the legislature for the last nine years as governor and before that as speaker of the House.

"Out-of-sight, out-of-mind," Sen. Joseph S. Bonvegna (D-Baltimore) said of Mandel, who was suspended from office after his sentencing on political corruption charges in October. "I haven't heard a word about him. I guess that's just the way of life."

"I haven't heard his name mentioned," said Sen. Frederick C. Malkus (D-Eastern Shore), who worked along-side Mandel for more than two decades. "It's like when one of us loses an election. Now what everyone wants to find out is what Blair Lee is all about."

For Lee, this session gives him an opportunity to place his own stamp on the Assembly after working for years in the shadow of Mandel. If Lee succeeds, he can go into next fall's Democratic primary with the image of a strong leader who gets things done.

From the first gavel to the last, this session will be a metaphor for the gubernatorial election. It will serve as an early elimination race, a sorting out process in the already crowded field of Democratic candidates for chief executive.

Hoyer finds himself wearing two hats - one as Senate president with the power to move and block administration bills, the other as a gubernatorial candidate whose own political fortunes could rise and fall with the successes or failures of the acting governor.

If he cooperates with Lee as he has with Mandels administration, Hoyer improves Lee's prospects as a gubernatorial candidate. If he opposes Lee's bills, on the other hand, the young senator from Prince George's County risks being stamped a political opportunist.

While Lee and Hoyer play out their political drama in Annapolis, no less than six other Maryland political figures who are not connected with the legislature will be closely watching.The six have expressed varying degrees of interest in challenging front-runner Lee for the top spot.

Attorney General Francis B. Burch, who showed up today and posed for photographers, is keying his strategy to a large-scale failure by Lee. If the acting governor falls on his face in the next 90 days, Burch believes, he (Burch) will become the favorite of Old Guard money and support.

In the meantime, Burch has little more to do than lie back and watch the session unfold.His legal opinions on such issues as property tax reform, corporal punishment and abortion will figure into the legislature's business and give him a chance to keep his name alive.

Another Lee challenger Baltimore County Executive Theodore G. Venatoulis, is expected to keep as much distance from Annapolis as possible. Not only does Venetoulis cast himself as a candidate unfettered by State House deals, he has little influence within his own county delegation.

The strategies of other potential and real gubernatorial candidates - former Transportation Secretary Harry R. Hughes , Baltimore Mayor William Donald Schaefer, Baltimore City Council President Walter S. Orlinsky and State Comptroller Louis L. Goldstein - will be influenced by Lee's and Hoyer's performances.

The election-year atmosphere was thick even on the first day of work. Members of the House took turns posing for pictures with U.S. Sen. Paul S. Sarbanes (D-Md.), a popular statewide figure who got his start in the Maryland General Assembly.

At times, the tone changed to political pranksterism. For example, House Majority Leader John S. Arnick (D-Baltimore County) showed off a white T-shirt with the lettering "Arnick for Speaker." Then, he displayed a black T-shirt with white lettering "Briscoe (who is now speaker) for Judge."

Among the more serious actions of the day was the Senate's overwhelming 36-to-6 vote to override Mandel's veto on the welfare bill, a bill that would have mandated the state to pay families in the aid to dependent children program the full amount they would need to have a subsistence standard of living, as established by the state secretary of human resources.

Current state law allows this program to be funded at 81.5 of this standard, and Mandel noted in his veto message last year that this could add more than $37 million to the statebudget annually.