For 15 minutes, Democratic gubernatorial candidate Stephen H. Sachs had been trying to sell skeptical members of a Salisbury Democratic club on his proposal that would raise Maryland's 5-cent sales tax a penny to boost education spending by $250 million a year.

Sachs, a two-term state attorney general with a flair for compelling rhetoric, was selling hard, but the Wicomico County Democratic Club did not appear in the mood to buy.

Then Sachs weighed in with his frog story.

The condition of education in Maryland is so precarious, argued Sachs, that biology classes at Wicomico County Senior High School have been using the same dissected frog the past eight years. "What possibly could be left of the same frog after eight years?" asked Sachs. The meeting room at the Knights of Columbus hall rocked with laughter.

Whether the frog tale is enough to persuade Wicomico County residents -- who are already facing a 25 percent increase in their property taxes -- to support a candidate who wants to boost sales taxes by 20 percent will not be known for 4 1/2 months. But it certainly brought the point home.

To the Sachs campaign, trailing badly behind Baltimore Mayor William Donald Schaefer in the race for the Democratic nomination, that is the hidden beauty of the education plan that is the centerpiece of the attorney general's campaign.

"Education," said Sachs campaign manager Blair Lee IV, "reaches into every single household. It's a fundamental, cornerstone service from government."

After a week on the road, the Sachs tax appears to be meeting, at best, mixed reviews. Many voters seem to be receptive to the candidate's arguments about the needs of education but reluctant to endorse the tax. Others are willing to embrace the tax but argue that it was the height of political folly for Sachs to propose it. Still others maintain that an increase in the sales tax would be unfair to poor people.

In campaign appearances in Carroll and Wicomico counties and on a Baltimore radio talk show last week, and in paid radio spots that will expand to television next week, Sachs has begun to take his case to the voters.

Boiled down to its essential elements, the pitch goes like this: Maryland, a comparatively wealthy state, is not spending enough state dollars on education. Local school systems are plagued by shortages of teachers and materials. Teachers suffer from low salaries, bad working conditions and poor morale. The lack of excellence in education compounds already serious social problems such as drug abuse and welfare dependency, and it hinders economic development. Maryland is falling behind more "vibrant" states such as Texas and North Carolina that put a higher premium on their schools.

This "crisis" in education, argues Sachs, can be addressed only by a massive infusion of state dollars, the majority of them earmarked for teacher salaries but significant amounts targeted to early childhood education, work programs for high school graduates who do not go on to college, and innovative programs to make schools better places to learn.

The Sachs tax has a couple of virtues. For one, it provides a forum to highlight what Sachs perceives is a Schaefer weakness. In his stump speech on the education proposal, Sachs pointedly mentions that the Baltimore school system was so short of teachers this year that it had to hire 30 instructors who had failed to pass the city's writing test for teachers.

Also, everywhere he goes, Sachs can point to local examples of the need for stronger and more effective schools.

In Wicomico County, it was an 8-year-old frog, a fact confirmed by a biology teacher who said he has kept the well-preserved amphibian as a "display" model because he cannot get sufficient funds to purchase similar large frogs for his students, who share and dissect smaller species of frog. The teacher said his students also lacked rubber lab gloves until a local undertaker donated some.

In Carroll County Sachs dramatized the teacher shortage when he asked how many in a group of 50 Western Maryland College students aspired to be teachers. Two raised their hands.

Among the negative reactions Sachs has received, many are from politicians, but not all:

*"Personally, I don't care for the sales tax," said Roger Mann, a former Carroll County commissioner and strong Sachs supporter, after listening to the proposal at a luncheon last week with local lawyers in Westminster. Mann, a small businessman who salutes Sachs for making education the focal point of his campaign, said the tax proposal is meeting "a little bit of static" in conservative Carroll County.

*"I don't want to comment on that," said Henry Parker, a Wicomico County Council member who sported a Sachs lapel sticker while listening to the candidate Wednesday night in Salisbury.

*"I think I fit in that group that says they don't oppose it, but politically it's chancy," said William Nagel, the president of the Wicomico County School Board. "I think it's courageous, but I voted for Mondale."

*"I'd like to vote for you, but I have a problem with this 1-cent tax for education," said one caller to a WBAL radio call-in show that featured Sachs on Tuesday night.

Others, however, are wholeheartedly enthusiastic about the proposal:

*Shaking hands in a London Fog plant in Carroll County, Sachs came across Roberta Buckner, 33, an examiner in the returns department, who told him, "I don't mind paying for a better education."

*In Salisbury, guard Joe Batter hailed the Sachs plan as "a good idea because teachers are underpaid all through the state."

Sachs characterizes the reception so far as more positive than he had expected. "I had expected a season of all negatives . . . but there is less of that than I expected from real people. Plus, there has been a lot of positive mail, pats on the back.

"It's like a jury," he continued. "There's a jury of 4 million people, and I have a case to make."

To reach that jury, the Sachs campaign bought radio time on 23 stations around the state. The 60-second spots, which urge voters to "consider the cost of ignorance," began Wednesday and will run through April 27. Beginning this Wednesday, similar television ads will appear in Baltimore and Washington markets. Viewers will see an ad that begins in silence with the following written message: "There are thousands of children in Maryland who can't do what you're doing right now. Reading."

The Maryland politicians who deride Sachs' tax proposal, including Schaefer, say it is unnecessary given the state's robust financial prospects. But campaign manager Lee says it has brought to the attorney general's campaign a flesh-and-blood focus that the campaign lacked despite months of hammering away at the enormously popular Schaefer.

"We've been searching for a way to make that case," said Lee. "This is it. We're on the high wire, we know that, but it feels good. He's not running against Schaefer anymore, he's running against ignorance . . . . People now know who Steve Sachs is. Almost overnight, who he is and what kind of guy he is has been defined through this package, for better or for worse."

For Sachs, the education proposal represents an issue that he is passionate about and one that he is comfortable running on. "This comes naturally; this is fun," he said.

Still, Sachs is dogged by suggestions that his endorsement of a tax increase in an election year represents a political kamikaze run. Everywhere he goes, he faces the ghost of Walter Mondale, who called for a tax increase to reduce the federal deficit in 1984 but found that the American electorate had little stomach for such candor.

In response to a comment from the host at his Baltimore radio appearance last week, Sachs dismissed the Mondale analgoy analogy as "nonsense" because the Democratic presidential candidate was had been talking about a vague concept that had little real impact on voters. "What's a deficit look like?" asked Sachs. "Can you touch it? Can you feel it? Did your mother-in-law teach a deficit? Schools are different. Schools are our children. We know what the value of a teacher is who can open up minds."

And to suggestions that he should have made education the centerpiece of his campaign without proposing a tax, Sachs responded: "If I'd done that I would have been just another politician saying exactly what people think politicians say, which is what people want to hear. If I had talked about how we have to do great things for education but not about how to pay for it, I would be a phony."

Some people question whether, on Sept. 9, Sachs will turn out to be forthright, and a loser. Campaign manager Lee said that more than one person has recently reminded him of Adlai Stevenson's remark when told that all "thinking people" would support his presidential bid: "That's not enough, I need a majority."