The General Assembly moved to within one perfunctory vote today of increasing the minimum drinking age in Maryland to 21, even though some of the staunchest supporters of the legislation say it may not reduce highway deaths caused by drunken drivers, or stop teen-agers from drinking or even be enforced by police.

"This is not a drunk-driving bill," said Sen. Jerome F. Connell Sr.(D-Anne Arundel) today, admitting that he was casting "a political vote" in raising the minimum legal drinking age from 18 to 21. Asked if the bill would save lives, which is one of its goals, Connell said, "Hell, no."

Connell said he and many of his colleagues voted for the bill today because of "the publicity, the newspapers. The governor's behind it."

Today's approval was on second reading. The Senate must approve the proposal one more time before it goes to Gov. Harry Hughes. But that final vote, which could occur anytime, is expected to be largely pro forma because today was the last time the bill could be amended.

When Hughes, a major backer of the emotional drive for its passage, signs the bill into law, effective July 1, it will reverse a 1974 legislative action that lowered the state's minimum drinking age for beer and light wine to 18.

Even Jean Heald, the lobbyist for Mothers Against Drunk Drivers (MADD), was cautious about the immediate impact of the bill, predicting that "there won't be any greater enforcement of this than there was when I was a child drinking."

But "it's a step," she said. "It's somewhere between a Band-Aid and a tourniquet." A major benefit, she said, is that the often heated debate on the issue has increased "public awareness" of the problem of drunken drivers.

"It's a stampede," said Sen. Laurence Levitan (D-Montgomery), expressing the uneasiness of some senators who felt they were pressed into supporting the bill by a governor and legislative leaders who made its adoption a top priority in this election year. "It's a law that's not going to be enforced."

Levitan was one of many senators who sought to limit the increased age to 19, arguing that the more modest change would have stopped the "trickle down" of alcohol to high schools students. One of the major complaints about the 18-year-old limit was that legal high school drinkers pass beer and wine down to younger students.

But Levitan said, "This year it's bigger than that--it's turned into a drunk-driving issue."

"Drunk driving is a real red herring," said Sen. Victor L. Crawford (D-Montgomery). "It raising the age was to get alcohol out of the schools. I was for 19 because we've got to raise the age. The 18-year-olds have been irresponsible about buying it for young kids."

"They're mixing this up with drunk driving," added Sen. Edward P. Thomas (R-Frederick). "It's mixing apples and oranges."

"It's a good year for it," said Sen. Tommie Broadwater, Jr. (D-Prince George's). "There's a law-and-order mentality this year."

Heald said MADD switched its lobbying emphasis from drinking by students to drunk driving after she saw the statistics from other states that had raised their drinking ages. She said the Insurance Institute for Highway Safety reported an average 28 percent reduction in traffic deaths in those states that raised their drinking ages after lowering them in the mid-1970s.

Hughes personally lobbied legislators who were wavering or leaning toward the setting the limit at 19, telling them his own poll showed a vast majority of the public favored 21.

An indication that some senators do not expect the law to be enforced came earlier today when they rejected by a whopping 26-to-17 vote an amendment that would have increased the $1 penalty for using false identification to purchase alcohol.

Sen. Clarence M. Mitchell, III (D-Baltimore) called the rejection of that amendment "the height of hypocrisy."

There is no easy way to tell how well the current drinking-age law is being enforced.

Sen. Thomas Patrick O'Reilly (D-Prince George's) said that in his county, the Board of Liquor Commissioners "strictly enforces" the law, staging "lots of busts" at establishments serving youths. But that effort is directed at tavern and liquor-store owners, not the young people who violate the law.

"I have never heard of a situation where violators of the law--meaning the minor--has been prosecuted," said O'Reilly, a lawyer.

A Maryland State Police official said today that in 1978, of 13,630 suspected drunk drivers who were given breathalizer tests, 1,552 were 18 to 20 years old, 239 were 16 or 17, and a dozen were 16.

"We're not going to put any more police on," Connell said. "We're not going to spend any more money to enforce it."

Sen. Julian L. Lapides (D-Baltimore), a supporter of the 21 age limit who opposed lowering it in 1974, said he, too, thought young people would still drink. "But if it's illegal, it puts the fun back in it for kids," he said. "So we're actually doing them a service." He paused, smiled and added, "I'm so perverse."