AT THE REPUBLICAN dinner table where I was a child, the political talk always included the litany evils assigned Franklin Roosevelt. FDR was a self-evident fraud. He bought votes with government handouts. Social Security deceived the people because it was not a true insurance program. The New Deal, for all its fanfare and largesse, failed to end the Depression. And so on.

In a narrow sense, these statements of Republican scorn were all crudely accurate, and yet our talk evaded the only relevant question. If these things were true about Roosevelt and the New Deal, when then did the people love him so much and reelect him so often? The answer was beyond the understanding of Republican households. Sooner or later, it was believed, the people would catch on to FDR's glib tricks, wake up to his arrogant deceptions, revile him and defeat him. That day never came, of course.

Only after Roosevelt's death could Republicans at last concede that -- like him or hate him -- FDR was a great leader.

So now we have a new president who would like to be mentioned in the same breath with FDR. Six months ago, I gagged on the thought. But I now believe the comparison is at least entitled to serious consideration. His young presidency has already turned American politics on its axis; it has created the preconditions for a new era which could realign the electorate and bind voters to a new set of loyalties.

Does that sound too grand? Of course, he may fail. Of course, he has been lucky. Of course, of course. I can write a plausible script outlining the economic disappointments and possible disasters which lie ahead for Reagan. I can predict foreign wars and swarms of locusts. Politics does deliver unforeseen crises, and surely Reagan will encounter his. But, right now, that sort of what-if forecasting obscures the historic nature of what Reagan has already accomplished. I am not sure political Washington yet grasps what has happened.Certainly his rivals don't, perhaps not even his allies.

Indeed, I can now imagine the children at Democratic dinner tables hearing a new litany of scorn for Reagan. He takes care of the rich and powerful while ignoring the weak and poor. He buys votes with special favors. His economic program, based on crank theory and hoary trickle-down Republicanism, won't deliver what it promises. You'll see -- Reaganomics won't work. All true, perhaps. But, like the Republican scorn for FDR, these complaints may not be of great consequence to future politics. In other words, like FDR, Reagan could well succeed politically even if his economics fail.

What has he wrought? That is the question which demands clear-eyed analysis. In ideological terms, President Reagan seems the negative image of President Roosevelt. As FDR ushered in a 50-year era of government centralization and growth, Reagan proposes to reverse that tide, to shrink the government and turn power and resources -- mainly in the form of money -- back to state and local governments and to private citizens. Given that stark framework, it is reasonable enough for liberals to assume that Reagan's ideology will fail, in time, as people make demands on the government for comfort and security.

But a closer comparison suggests the differences aren't that stark. From 1932 to 1940, FDR approximately doubled the federal government's share of the gross national product, then the war years pumped it up even more dramatically. As Reagan came to power, the federal sector expended roughly 21 percent of the GNP (about the same as in 1945), and his budget projections suggest that it might conceivably decline to 18 or 19 percent of the GNP, hardly the stuff of revolution.

My point is that, despite the thunder and lightning over the Reagan budget cuts this year, despite his own zealous rhetoric, Reagan's federal government is not getting smaller, but still growing larger. What Reagan has done in 1980 is slow down the federal government's rate of growth and presumably shrink its share of the expanding national economy. This is not insignificant or without real political pain but it is quite different from laissez-faire ideology which Democrats love to scorn. Reagan is not trying to roll the history books back to 1932. His target is more like 1960.

In fact, perhaps the most important lesson we should have learned in the last six months is that Reagan the politician, making choices and selling them, resembles in many ways the interest-group liberalism which FDR invented and conservative ideologues despite. Reagan chooses to reward different interest groups, a Republican list of clients, including some which used to belong to the Democratic Party, but the essence of his game is not so different from the one Roosevelt played with relish.

In the crunch, despite his ideological opposition, Reagan cuts a deal on Japanese imports to protect the American auto industry. He lets the farmers sell their grain to the communists. Under pressure from Boeing and General Electric, he relents on budget cuts for the Export-Import Bank which finances their overseas sales. In search of marginal votes in Congress, he accepts a sugar subsidy program that is odious to his free-market benefits. Needing more marginal votes to pass his tax bill, Reagan endorses the peanut allotment program he had intended to abolish. He easily gives a bundle of tax concessions to oil and another bundle to the savings and loan industry and another to widows and orphans who are fortunate enough to own oil wells.

The spectacle was offensive, a crass game of swapping and trading, totally without principle, the sort of rank behavior enraged true conservatives when Roosevelt and his deciples did it. In modern American politics, in this complicated democracy of competing interests, it is the way of winning politicians, the way they bind disparate groups to their banner for the next battle ahead.

That is the intriguing question: Which voters is Reagan binding to his banner? Which groups in the electorate is he converting to loyal followers? We know from the headlines who got hurt by the budget cuts. We know from the political rhetoric that the Reagan tax cut helped the rich and hurt the poor. But perhaps something more was occurring in the Reagan tax bill -- a pivotal event which might convert a vast middle group to the Republican banner.

I'm not sure, but here is a strategic analysis from the White House boiler room which seems at least plausible and maybe even right. The partisan debate focused on the interest-group payoffs of Reagan's tax bill and the trickle-interest-group payoffs of Reagan's tax bill and the trickle-down aspects of drastically reducing taxation for corporations as well as individuals with more than $50,000 annual income. But the three-year tax cuts also delivered real cuts to those families between $25,000 and $50,000 -- not gigantic reductions that will change their lives dramatically, but nonetheless real money, certainly more real than the biennial inflation tax cuts which Democratic Congresses have been handing out for the last 10 years.

These families are in the "new" middle class created by postwar prosperity; they are not your old-fashioned country club Republicans. Many families have two wage earners, both husband and wife working hard to stay even and feeling intensely cheated by inflation. The wife is a school teacher, the husband sells insurance or drives a truck. Perhaps they voted for Reagan in 1980, fed up with inflation and anxious for any kind of change, but they probably think of themselves as Democrats or independents.

The Reagan tax cut gives them something real in 1982 and 1983. What's more, the addition of indexation against inflation guarantees that they will be protected against future inflation, at least in terms of creeping taxes. Will they feel grateful to Reagan and the Republicans and reexamine their political loyalties? That is the implicit strategy of the Reagan tax cut.

If Reaganomics actually works -- that is, the economy booms and the era of high inflation ends -- then the Reagan banner will win, certainly, for a long time. But even if Reaganomics doesn't work, he has reached out to "buy" a huge bloc of voters, protecting these people in a way that may make them feel good about him, regardless. The way millions of Americans felt good about Roosevelt even though his social problems didn't end the Depression.

One might, in fact, define Reaganism in this way: protecting certain voter groups against the ravages of inflation and a stagnant economy, while exposing others to the pain. The "new" middle-class gets protection while federal benefits to the working poor, just below them, and the welfare poor shrink. In inflation continues while benefits stand still, it is a little like "de-indexing" for the needy pushing them forward to endure the sharp edges.

That sounds rather ugly to me, but not necessarily dumb politics. Indeed, it sounds like class welfare. It is, but of a different sort than liberal Democrats are used to playing. Reagan understands, as FDR did, that a president binds voter groups to his coalition by strong and inevitably divisive actions, not by the reassuring rhetoric of unity. It is a gamble, of course, but a plausible one. r

Now, thanks to the three-year tax cut and indexation, he has put the Congress on a collision course with its own spending habits. Denied the cushion of inflation-generated revenues, both Democrats and Republicans are going to discover shortly that the era of budget-cutting has only begun -- that they must wack away further at social programs, including Social Security and Medicare and Medicaid, as well as sacred cows like defense. They may decide instead to endure huge deficits. But it doesn't seem likely that they are going to raise taxes any time soon, certainly not the taxes of those earnest working families in the middle.

Thus, we are embarked on an extroardinary period of fractious, probably mean-spirited politics in which the different social classes contend directly in a way they have not for years.Reagan, one assumes, will be caricatured as a kind of reverse Roosevelt, taking from the poor to comfort the non-poor.That image could be quite damaging but, if Reagan minds what he is doing, he will make certain that the new middle group is protected. Hos economic policies may well fail, as so many predict. But his politics might just win anyway.