Watching the Democrats watch the Republican president stride triumphantly into the House of Representatives the other night was another vivid demonstration of how far the political wheel has turned.

Not so long ago, by history's clock, it was the Republicans who felt compelled to cheer the personal qualities of a charismatic Democratic president -- and yet were forced, like many congressional Democrats last week, to sit on stony, frustrated silence while he skillfully delivered his political message over their heads to the country.

No one expressed the old GOP plight better than that good Republican, and great editor from Kansas, William Allen White. When Franklin Delano Roosevelt was riding high, transforming American politics, and fashioning his majority coalition at the expense of the Republican Party, White gritted his teeth and wrote:

"Biting nails -- good, hard, bitter, Republican nails -- we are compelled to admit that Franklin Roosevelt is the most unaccountable . . . president that this United States has ever seen. He has added a vast impudent courgage to a vivid but constructive imagination, and he has displayed his capacity for statesmanship in the large and simple billboard language that the common people can understand; moreover, that the people admire, even when it is their deadly poison. We have got to hand it to him.

"Well, darn your smiling old picture, here it is! Here, reluctantly, amid seething and snorting, it is. We, who hate your gaudy guts, salute you."

Present political claims notwithstanding, Ronald Reagan is no Roosevelt. His approach to politics and the art of governance differ markedly from Roosevelt's, just as the conditions he confronts in the America of the 1980s in no way resemble what FDR faced in the Great Depression of the 1930s.

Unless he is an even better actor than we think, Reagan gives no indication of relishing the political intrigue and manipulation that were Roosevelt's hallmark. Nor does he seem to enjoy the intricacy of issues and the exercise of command as did his Democratic presidential predecessor. Even his personal characteristics are not comparable to those of Roosevelt, though that analogy has been drawn often in these first three months of the Reagan presidency.

FDR inspired love and adulation as probably no president since Lincoln. But, as William Allen White's words remind us, he also stirred another deep public emotion -- hatred.

It's inconceivable to think of people hating Ronald Reagan. He is the most genial of public figures. His very likability has become the political cliche of the decade. In an age when our presidents increasingly try to be more informal -- plain Jimmy follows good old Jerry -- his call-me--Ronnie manner is the most appealing of all.

Yet despite all their differences, a powerful political connection exists between Roosevelt and Reagan.

Franklin Roosevelt was able to translate his immense popularity into success for his party; from minority status, the Democrats became the majority force that ruled the nation for half a century. The historic stakes for Reagan and the Republicans are equally high.

Reagan's popularity, at present perhaps unequalled since those early New Deal days of FDR, gives him an opportunity to refashion the American political landscape as dramatically as Roosevelt. But he will not do it by charm alone, any more than FDR did.

The Roosevelt Revolution occurred because force of personality was coupled with tangible political success. The New Deal worked. It launched the United States into its most productive period. Whether measured socially, economically, militarily, or politically, the nation that emerged from the Roosevelt era was stronger in every respect. The Reagan Revolution that already is being hailed as historic fact in some corners ("The Reagan Revolution -- American Renewal," is how the Republican National Committee titles a publication) could have the same kinds of political results if the president's program works.

It is, to use Churchill's phrase, a "terrible If."

Reagan and the Republicans stand today on a dizzying height. If their economic program performs a they promise us it will, with all the conviction of the true believer, they will be on the way to becoming the majority political force, quite likely for the rest of this century. Those are the rewards of success. But if it fails, as some critics say inevitably it must, leading to greater inflation, soaring interest rates and mounting government deficits, they certainly will be headed toward political oblivion. Those are the consequences of failure. Either way, the risks are great.

You have to hand it to Ronald Reagan. Like FDR before him, he moves boldly. Whether his political place will turn out to be as high as the Democratic Roosevelt no one can say. Three months do not make a presidency, and one speech, no matter how extravagantly cheered and praised by politicians and members of the press, does not signal success for an administration. For the moment, though, something else william Allen White said of FDR now applies to Reagan.

"As you know, I have never been greatly excited about Roosevelt as a dictator," White wrote to a friend. "He laughs too easily. He is too soft-hearted in many ways. . . . But he has functioned much like a dictator in chopping off the political heads of possible rivals -- not with a snickersnee, not with a machine gun, but with soft soap, kicking them upstairs or choking them to death on taffy."

Which is just about what Ronnie Reagan has been doing to the Democrats of late.