As Democratic presidential hopeful Sen. Paul Simon's standing in the polls has risen, so has interest in the core of his platform: enacting a broad array of domestic spending programs, adding little or nothing in new taxes, cutting defense spending only modestly, and still balancing the budget within three years.

The Illinoisan, who calls himself a "pay-as-you-go" Democrat, is the only presidential candidate of either party who says it can be done.

"Neo-voodoo," responds Steve Murphy, Rep. Richard A. Gephardt's Iowa campaign manager.

"As best we can cost it out, he is moving in the direction of larger budget deficits," says Bart Gellman, former Arizona governor Bruce Babbitt's issues coordinator.

Simon is unswayed. "I am going to move on it and move on it immediately," he said yesterday in New York of his pledge to balance the budget by 1991. "It is inconsistent to be for social programs and not be for a balanced budget."

How to get there? In a speech his aides had billed as the first step toward providing an answer, Simon gave an audience of 700 New Yorkers few new details. "His style was terrific, the best I've seen of this year's candidates," said one prominent New York businessman and political activist, who asked not to be identified, "but his lack of substance was appalling."

Simon used administration figures to project a $91 billion deficit for what would be his third year in office, the year he says he would balance the budget. He said he would attack it with $10 billion to $20 billion in defense cuts, though he added that they would be offset by his proposed increases on the domestic side. (Critics say they would be offset several times over.)

In Simon's formulation, then, all of the $91 billion would have to come from budget savings he said would accrue from lowering unemployment by 1.5 percentage points and reducing interest rates by 2 percentage points. He did not spell out how he would produce these macro-economic improvements.

Of taxes, he said, "as a last resort, a small increase might be necessary, but I do not think they will be necessary."

Simon's lack of specificity on the cost-cutting side is matched by his disinclination to place a price tag on most of the dozens of new domestic programs he has proposed as a presidential candidate. His press secretary, Terry Michael, cautioned against taking all of Simon's proposals too literally. "He's not for open-ended spending for a laundry list of programs . . . . You throw out a lot of ideas in a campaign, but when you implement them, you are a practical politician. You do what you can create a consensus for."

On the stump and in his campaign literature, Simon strikes a different tone. "I stand for using the tools of government to move on our problems, and I don't shy away from that," he says. Yesterday, he told the New York audience: "I embrace our tradition of caring not just with words, but with my whole heart. . . . "

Among the proposals Simon has made in his campaign speeches or literature:A guaranteed job opportunity program that would provide public-sector minimum-wage jobs -- "building bicycle paths, tutoring the illiterate, working in day-care centers, cleaning ditches along rural roads, repairing sidewalks, tearing down condemned buildings, cleaning up neglected cemeteries, cleaning up trash along highways, insulating homes for senior citizens, planting seedlings" -- to at least 3 million Americans who are currently unemployed. Simon has introduced a bill that would cost $8 billion a year, though critics say it would cost triple that to fulfill the goals he has set. "I think he's taking on an important problem but it's likely to be more expensive and produce fewer new jobs than he assumes," said Isabel Sawhill, an economist at the Urban Institute.

Expanded college student loan programs. (He has opposed the Reagan administration's $4.1 billion in cuts.) No cost estimate.

Expanding federal support for early childhood programs. No cost estimate.

Federal funds for local school districts to teach new math, science and foreign language courses. No cost estimate.

"All-out attack" on adult illiteracy. No cost estimate.

Tax incentives for corporations to enagage in job-producing research and development. No cost estimate.

$2 billion in AIDS research and education, four times current expenditure and twice that for the next fiscal year.

A $5 billion a year long-term health care bill introduced this year -- with Simon as cosponsor -- that would be funded by removing the cap on the Medicare payroll tax (1.45 percent) for Americans who earn more than $45,000.

Free hearing aids, dentures, etc., provided by the federal government for the elderly. No cost estimate.

Simon also:

Calls for the federal government to "move quickly" on ground water protection, acid rain, depletion of the ozone layer, and desalination. No cost estimate.

Says that federal employes' pay and pensions should be protected against deficit reduction measures.

Talks of the need to at least partially restore the Investment Tax Credit (a $24 billion a year tax expenditure) and restore general revenue sharing. No specifics.

Supports reduced interest rates for farmers, and federal efforts to encourage use of corn ethanol in gasoline, No cost estimate.

Cosponsored legislation that would make maternity- and child-care leaves the law of the land.

Cosponsored a bill to increase the amount of child care costs deductible from federal taxes.

Cosponsored legislation to fund emergency shelters for victims of domestic violence.

In his 1987 book, "Let's Put America Back to Work," proposes a 6 cent-a-gallon gasoline tax to pay for the $7 billion rebuilding of rural roads, highways and mass transit, proposes spending another $7 billion on water and sewer system repair, with revenue to come from "natural growth" of the federal budget, or from alcohol and cigarette taxes, which he has supported in the past but declines to commit himself to now.

In same book, calls for an American Conservation Corps, in which young people would help spruce up the national parks and forests. Estimated cost: $200 million.

In same book, calls for a 2 percent surcharge on all long distance calls to provide free phones to the estimated 7 million Americans who don't have any. All the phones would have to be manufactured by domestic labor, providing jobs, the book notes, for the International Brotherhood of Electrical Workers and the Communication Workers of America.

In an interview yesterday following his speech, Simon bristled at the suggestion that, in a manner somewhat reminiscent of Ronald Reagan's 1980 campaign, he was asking the American people to accept on faith the idea that he could carry out his spending proposals, holding the line on taxes and still balance the budget. "The difference is that Ronald Reagan didn't know what he was talking about. He didn't know a budget from a kangaroo. I do."

He added: "The very fact that you have somebody in charge who knows what he's doing, is going to instill confidence in the financial markets. I think that alone will drop interest rates down."

And he promised that more details would be forthcoming. "I have to leave you at least one story to write," he said, "between now and next November."