In the country, we have not yet quite got rid of the Roosevelt generation. Like me, Ronald Reagan came of age in 1932. That year he cast his first vote - for Roosevelt. He also voted for FDR in 1936, 1940, and 1944. Recently, however, he has been less faithful.
What happened to him? Nothing, perhaps. You may remember that principle of personal political development enunciated by the late, great Professor Arthur Norman Holcombe: ''A conservative,'' he used to say, ''is a person who was a liberal when young and has not changed his mind.''
Yet President Reagan retains much of the Roosevelt heritage. As for activism, in foreign affairs his commitment to government intervention could hardly be more pronounced; and as for spending, national defense, it seems, is more than ever regarded as an area of policy where problems can be solved by ''throwing money at them.'' In consequence, indeed, the undeclared Keynesianism of this administration is propelling the economic recovery, such as it is, of the whole of the West.
But especially Reagan's conception and use of the presidency is Rooseveltian, as he would be the first to admit. He is certainly not, as we used to say in Gov 1, a ''Whig president,'' who sees his job as merely executing the laws that happen to be passed by constitutional process. He is more of a populist than FDR. Although in 1932 Roosevelt entered presidential primaries in eleven states, he campaigned in none of them for the nomination, but sent Jim Farley to work things out with the local notables. Reagan, on the contrary, won his nomination not by the ''peer review'' of Republican elites - who would surely have chosen Ford - but by winning 60 percent of the vote in 32 primaries. And thanks to his populism, Reagan has restored authority to the presidency.
President Reagan has not reversed but continued that nationalization of politics to which Roosevelt gave such impetus. He has not lessened the focus on Washington and the issues of politics as defined by the man in the White House. He has not resisted but responded to the trends that have cut back the role of the local notables and dispersed power among millions of activists - so massive that in 1980 some 30 million people voted in the presidential primaries, not to mention the very large numbers who took part in the caucus states.
It is a momentous development of that uniquely American contribution to political theory, the doctrine of popular sovereignty.
Half a century ago Franklin Roosevelt coped with the class and economic divisions of his time, including the excluded and making the nation more of a nation. Today our most disruptive divisions are cultural, ethnic, and racial.
The continuing nationalization of American politics has brought these diversities into often abrasive confrontation. In this situation there is both challenge and opportunity. On the one hand, the country seems bigger and more impersonal, setting us apart from each other and thinning the old bonds of public affection. On the other hand, technologies that bring together ideas and people have made the nation seem smaller and more aware of itself.
Where will we find the new nationalism to take advantage of the opportunity to meet the challenge? Can Reagan's conservatism cope with the new diversities as well as Roosevelt's liberalism coped with the old? I doubt it.
In any case let me emphasize that I am not asking him to feed us pap from National Brotherhood Week. The American Union thrives on controversy and dissent. As any member of the Roosevelt generation can tell you.
Excerpted from the September-October Harvard Magazine. Samuel H. Beer, Eaton professor of government at Harvard University, is working on a book, ''Federalism and the National Idea.''