In the largely unexplored terrain where economic policy alters the partisan political balance, President Reagan may turn out to have won a lot more from the Democrats than some tax and budget cuts.

The federal tax and benefit structures have both been altered by the 97th Congress in ways that could have enormous long-term political consequences.

First, with surprisingly little debate Congress took a revolutionary step long advocated by Republicans; it voted to limit government growth through what amount to permanent tax cuts out into the future. For the next three years individual income tax rates will be reduced 25 percent in every bracket; thereafter the tax code will be indexed or adjusted automatically each year to offset the tax-increasing effect of inflation. Unless the Reagan economic program produces a revival far exceeding the forecasts of even the most optimistic supply-siders, this tax bill will thus eventually force a deficit-minded Congress to make even more spending cuts than it already has, not put programs back as some Democrats hope. In effect, the administration has succeeded in placing a fiscal noose on Democrats that will not be loosened even if the party regains control of the federal government.

Second, Congress significantly narrowed the base of the federal tax structure. In a bill that heavily rewarded traditional Republican constituencies, it sharply reduced and in some cases nearly eliminated federal taxes on such forms of income as business profits, capital gains, interest income and oil revenues, as well as on inheritances. In doing so, it left the government more dependent than ever on taxes on ordinary wage and salary income. This could put the Democrats in a quandary if they move to increase taxes to restore spending programs in the future. To build back programs for some of their constituents, they will have to increase taxes on others. Unless they can revive some of the taxes that Congress nearly wiped out this year, to help welfare mothers they will have to tax factory workers. There is no political joy in that.

A third point has to do with middle-income taxpayers, those in the $25,000 to $40,000 range. This is a swing group to which Democrats have primarily appealed in the past. But in this year's bill the Republicans appealed heavily to such taxpayers, whose incomes and tax brackets have risen with inflation, claiming, in effect, "We can match Democrats." The Republicans moved to supplant the Democrats as the tax champions of the middle class. The ability of the GOP to translate tax policy into voter allegiance is unknown.

Fourth, the cuts in social programs not only reduce federal spending for the poor, an essentially Democratic constituency; the people running these programs who stand to lose their jobs are also largely Democrats, in many cases active supporters of the party.

Some liberal to moderate Democrats have professed to be happy they lost on the tax and spending votes. Reagan is now responsible for the economy, and these Democrats believe the Reagan economic policy will fall flat on its face. In the subsequent rising unemployment and continuing inflation, according to this scenario, voters will return to the Democratic fold.

In the words of Sen. Thomas F. Eagleton (D-Mo.) during the Senate debate on the tax cut: "This bill keeps the Democratic Party alive. It is so inherently inequitable, so inherently unbalanced, so inherently unfair that it will stand as a bedrock for the rebirth of the Democratic Party."

This strategy was advocated on the budget side by Rep. David R. Obey (D-Wis.), who contended that instead of putting up a fight, the Democratic-controlled House ought agreeably to give President Reagan what he wanted. Democrats could then sit back as the political time bombs in the budget -- fewer college loans for middle class students, costlier school lunches, no more Social Security minimum benefits, to name a few -- began to explode inside the Republican lines. Eventually, so the theory goes, this will help revive the fundamental Democratic belief that government has an essential role in maintaining the general welfare.

This view of the future fails, however, to recognize an alternative scenario in which, even if Reagan economics does collapse, the altered tax structure, and to a lesser extent the substantive changes in spending programs, will make it very difficult for a hypothetically revived Democratic Party to reassert its support for programs important to the Northeast and the Midwest, where loyalities remain strongest.

For the Republicans, the tax and budget bills were remarkable political accomplishments.

Not only did the $749 billion tax cut -- particularly indexation starting in 1985 -- go a long way toward the Republican objective of restricting future federal growth, but the tax legislation significantly altered the tax burden in a fashion furthering GOP partisan interests.

The tax bill will accelerate a long-term trend toward what is almost a phase-out of the corporate income tax. In 1940, this tax on profits provided 30.5 percent of federal revenues; in 1950, 34.3 percent; in 1960 it dropped to 22.3 percent; in 1970 it was 16 percent and this year 12.4 percent.

With the passage of the tax bill and the provisions effectively ending taxation on income from new investments, the administration foresees revenues from the corporate income tax remaining basically static through 1986, while total federal revenues increase from $520 billion in 1980 to $923 billion in 1986. This would leave the corporate income tax providing 8.1 percent of federal revenues.

While there is an extensive debate among economists over who ultimately pays the corporate income tax (consumers, shareholders, employes in lost wages, or others), it is first felt by the corporation and its stockholders, who tend to be among the well-to-do.

Similarly, aside from the across-the-board rate cuts, most of the "sweeteners" added to the tax bill are directed to the rich. Oil tax breaks total $11.7 billion through 1986; new savings certificates and new interest exemptions, which are advantageous only to those in high tax brackets and with large amounts of money earning interest, total $7.6 billion; the near-elimination of the estate tax, which will exclusively benefit heirs to very large estates, will amount to $15.3 billion. The reduction of the maximum rate on unearned or investment income, and the associated cut in the capital gains rate, will also benefit almost entirely those with incomes above $50,000, at a cost to the Treasury of about $15 billion.

Translating these fiscal shifts into political terms, the Reagan tax bill targets benefits to predominantly Republican constituencies. Taking just persons with incomes above $35,000, a May, 1981, Associated Press-NBC poll found that 53 percent were Republican, compared with 31 percent Democratic. The figures are even higher above the $50,000 mark. (In contrast, the poll found that persons earning from $8,000 to $15,000 were 43 percent Democratic and 39 percent Republican.)

At the bottom end of the income scale, figures compiled by the Joint Committee on Taxation show that -- when already scheduled Social Security tax increases are taken into account, plus inflation's effect in pushing taxpayers into higher brackets -- those earning $20,000 or less, a majority of tax filers, will face a net tax increase in 1984.

This group of tax filers, who are also the strongest supporters of the Democratic Party, is expected to submit 42.5 million returns to the Internal Revenue Service this year out of 77.2 million, or 55 percent of the total. According to the joint committee, persons in these low (and largely Democratic) income brackets will end up paying $4.5 billion more in taxes in 1984 when inflation and Social Security increases are taken into account.

By the same accounting standard, the tax savings for those making more than $20,000 will be $16.2 billion in 1984. These totals do not reflect the distribution to income groups of the changes in the estate tax, savings certificates, exclusions on income earned overseas, the oil tax cuts and the interest exclusions, all of which directly or indirectly (some are not part of the income tax) function to increase the disparity in the distribution of the breaks in the tax bill.

Again, translating these statistics into political terms, the Reagan administration has succeeded in keeping what might be described as tax pressure on the income group from which liberal and moderate Democrats must receive maximum support in order to win elections. The group this wing of the Democratic Party must persuade to go to the polls in support of candidates advocating restoration of social programs is precisely that part of the electorate receiving little or no tax relief.

In effect, there will be a tax disincentive to support restoration of social programs among those making less than $20,000 a year. In contrast, those from upper-income groups that have generally supported the GOP in the past will have received a tax reward for that support, further reinforcing the partisan tie.

For those in the middle ground -- $20,000 to $35,000 -- the Reagan administration has succeeded in blurring, if not blunting, the traditional appeal of the Democrats. They do achieve a net tax reduction after the effects of Social Security and inflation are taken into account, although it is not as significant as the net cut for those in the upper brackets.

In coming elections and in future legislative strategies, these tax shifts will be one of many factors. Another major element will be the political consequences of the budget cuts.

Democrats are already attempting to develop maximum political capital out of the GOP proposal to end the $122 minimum Social Security benefit, the danger of which President Reagan has recognized and now appears ready to lessen through compromise. Other cuts with strong political potential for the Democrats are in the college loan program and school lunches, both of which will place additional burdens on the middle class, the swing group in elections.

At the same time, however, most of the cuts are not only in programs that provide services to the poor, a largely Democratic group with a poor turnout record on election day, but also in programs whose employes are largely Democrats. Not many Republicans are on food stamps; that is the political shorthand of the budget cuts, and both parties know it.

Not only in Frostbelt cities from Baltimore to Los Angeles, but throughout the Sunbelt, these programs provide employment for Democratic party activists, the men and women who ring doorbells, pass out leaflets and run telephone banks before election. In the middle of the budget fight, Sen. Pete V. Domenici (R-N.M.) went back to to the Zapata Club in Albuquerque to meet with 50 of the workers in the programs facing reductions."There might have been one Republican out of 50 there," Domenici noted. Although it is not possible to determine the number of workers who will be put out of work as a result of the cuts, it is clear that they will include far more Democrats than Republicans.