Jimmy Carter and Gerald R. Ford, two former presidents of the United States, published a joint article in the Reader's Digest this month. The subject was ''A time for courage in the Middle East.'' In a friendly appearance in Ann Arbor, Mich., Feb. 9 the two again joined forces; they took issue with charges that they are responsible for the $207 billion budget deficit under the Reagan administration. The new relationship seems to be broadening. The two former rivals say they have become close friends since they opposed each other in the 1976 election. It began when America's three living ex-presidents, including Richard Nixon, flew together in October 1981 to Cairo as part of the US delegation to the funeral of Anwar Sadat, the president of Egypt, who was assassinated.
The relationship inevitably recalls another famous political reconciliation in American history. Observers wonder how far it will go. Thomas Jefferson defeated John Adams in the presidential election of 1800. The nation's second and third presidents became estranged. Until then they had carried on a voluminous correspondence; suddenly it ceased.
There aren't very many former presidents in American public life. Their potentiality for leadership is often forgotten. Herbert Hoover, for example, left the capital in a storm of unpopularity fifty years ago. Then after a dozen years Harry Truman brought him back and put him to work. He did splendid service as head of commissions to study reorganization of the executive branch of the government. It is too bad that there is not more of that bipartisan cooperation today.
As for Jefferson and Adams they were brought together by the intercession of the kindly Philadelphian Dr. Benjamin Rush. Adams was living in Quincy, Mass., Jefferson at Monticello. Wasn't it about time that they resumed their former friendship they were asked? ''I always loved Jefferson,'' Adams responded impulsively, ''and still love him.'' It was only a question of time after that. As Dumas Malone, the chronicler of ''Jefferson and His Time,'' puts it, they ''reopened the dialogue which was to enrich the rest of his life and that of his correspondent, and the record of which was to prove a priceless gift to posterity.''
Is there a parallel between then and now? Not in ease of communication. It doesn't take so long for Messrs Ford and Carter to reach understandings. At one point about 1813, Jefferson is pleased with the speedy transmission in the resumed Quincy-Monticello correspondence - only seven or eight days.
''Employing their respective talents,'' writes Mr. Malone, ''he and Adams had supplemented each other well (in preparing the Declaration of Independence). What the skilled literary craftsman from Virginia wrote was staunchly and successfully supported in crucial debate by the forceful delegate from Massachusetts. The former always looked back on this as the most memorable occasion in his public life, and he never forgot his fellow members of the class of 1776. In the first of his letters to Adams he lamented that so few of the signers of the Declaration were left. Among them, for services at the birth of the Republic, he always placed Adams first as that patriot surely knew.''
What do Messrs Ford and Carter have in common that now seems to draw them together? True they belong to rival parties as Adams and Jefferson did. But they share the unique experience of having had enormous power as head of the government and of now being private figures without portfolio. It always seems extraordinary to me that America does not make formal use of its retired presidents. Under most democratic systems they would automatically be in the cabinet, or in the front rank of the opposition. Here they have an ambiguous position. Messrs Ford and Carter have broken out of the mold by their joint comments on the Middle East. It amounts to a criticism of Prime Minister Menachem Begin's tough line. They are also drawn together by a defense of their economic record against the charge that they created the stupendous federal deficit. But more important than all this, probably, is the shared loneliness of their former power. They actually have sat in the Oval Office.