SENATORS Helms and East are firmly against the increased gasoline tax, they explain, because it bears too heavily on the poor. Last August, they were against the big income tax bill because it bore too heavily on investment -- i.e., business and the rich. Their position on revenue seems to be that they are against it.

How about the other side of the budget? They fervently denounce large deficits. But they do not seem to feel that any very large reductions in defense spending are possible. Nor are they calling audibly for cuts in Social Security. Owing to the well-known fact that the virtue and prosperity of the Republic rest upon the shoulders of the sturdy yeoman farmer, not a hand is to be laid upon the agricultural subsidies -- least of all the tobacco crop restrictions. What does that leave to be adjusted downward? Ah, yes -- food stamps, again.

North Carolina is not what you might think from the Helms-East performance. Its population is, in most things, sensible and good-hearted. The state is noted for its passion for public education, its fine universities and, among many other things, its first- rate newspapers. It is not the home of the mean and vindictive spirit that a casual observer of the Senate might easily infer. The two senators are opening themselves to a suit for libel brought by their state, on grounds that their activities are subjecting it to public contempt and ridicule.

But it's also true that the two North Carolinians are only the most extreme and raucous expression of a view of the federal budget that originates at the White House. That is the most important source of the idea that the country is entitled to a steady succession of tax reductions, to be balanced by cuts in "non-defense spending." The precise targets in "non-defense spending" become increasingly vague as people come to realize that the category consists principally of Social Security and Medicare, two subjects that the president currently refuses to touch.

But the interesting thing about the president's policy this year is that twice he has come to see that the country cannot persist with its present sadly diminished revenues, and that it has no alternative but to raise them. In July, after the Senate leadership got a major tax bill almost halfway through Congress over his opposition, he swung to its support -- energetically and skillfully. Similarly, he endorsed the gasoline tax last month only after the leaders of the House and Senate had jointly launched it.

Mr. Reagan wrote the music that seems to inspire the two North Carolinians. The difference between them is that the president, at the crucial moment, is capable of recognizing necessity and, rather gracefully, reversing himself. Senators Hems and East, still hearing that seductive music, are not.