When she recently jumped the fence to re-register as a Republican, Jeane Kirkpatrick bet a bundle on the good name of Ronald Reagan's foreign policy.

Now she's worried that sly revisionists are trying to pluck the feathers from her president's hat -- even insinuating, the cads, that Reagan's successes began with a belated swing toward Jimmy Carter's views.

Nonsense, she says, in a recent column. In the Carter years, as she puts it, ''half-a-dozen countries slid into the Soviet empire,'' while under Reagan there have been many victories for democracy, in ''El Salvador, Honduras, Guatemala, Bolivia, Brazil, Argentina, Uruguay, Grenada, the Philippines. . . .''

But wait. Argentina? The Philippines? Speaking of ''robbery in broad daylight''ju (her phrase), what did Ronald Reagan do in the way of democratic rainmaking in those places?

In fact, Jeane Kirkpatrick's credentials as an arbiter of these historical matters are most questionable to begin with. She backed the Argentine military junta, which was anything but democratic. Ditto, to a late hour, Ferdinand Marcos in the Philippines. More to the point, so did her president -- in both cases.

Speaking of robbing credit lines, it was Margaret Thatcher, not Ronald Reagan, who challenged the brazen grab of the Falklands by the Argentine generals, setting in motion the forces that led to their eventual ouster by Argentine democrats.

At the time of the Falklands crisis, in early 1982, Reagan telephoned Gen. Leopoldo Galtieri to beg him to desist. Galtieri contemptuously refused. It was Thatcher who then took on the dirty work while the president struck a high-toned pose of neutrality. Indeed, he seemed to have a tough time choosingju between Jeane Kirkpatrick's pro-Argentine sympathies and his secretary of state, Alex-ju ander Haig, who supported the British armada in the islands' repossession. Nicholas Hen-ju derson, British ambassador in Washington, said later that whenever Haig was out ofju town, the ''Latino lobby'' seemed to takeju over U.S. policy. That hardly suggests that Ronald Reagan was the strong man of the episode.

And what about the more recent developments in the Philippines? Please recall that Jeane Kirkpatrick first caught Ronald Reagan's fancy as the author of the famous article ''Dicatorships and Double Standards.'' She therein argued, rather persuasively, that when the United States faces dire alternatives, authoritarianism of the right is preferable to communism. Her argument, itself scholarly and subtle, fit the simpler Jesse Helms-Ronald Reagan world view like a glove, and they leapt like hungry trout at this certification by an authentic intellectual.

But when Marcos began to totter this year, the effects were felt. Reagan feared there was no daylight between Marcos and the communists. He wavered and waffled. Only when the defection of top Philippine military figures had all but guaranteed Corazon Aquino's success did Reagan get on board.

The omission of all this fine print makes Jeane Kirkpatrick's recent comparative history as ''revisionist'' as the kind she denounces.

And indeed, does her analysis really reach the core of the problem? American politicians have long made a habit of laying cheap, tendentious claims of credit for ''successes'' abroad, while seeking to blame the other party for ''failures.'' As history, this is childish and piddling stuff, whoever indulges in it. Jeane Kirkpatrick is historian enough to know it. From the ''fall of China'' in 1949 to the ''fall of the shah'' 30 years later, these remote events have generated tiresome breast-beating in Washington. But the breast-beating brings a useful understanding of the dynamics of history no nearer.

It is ''the illusion of American omnipotence,'' in D. W. Brogan's phrase, to think that American presidents have the leverage to manipulate revolutionary situations everywhere. It is unhistorical to insinuate that Carter bore responsibility for the fall of the shah or to give Ronald Reagan credit for more favorable turns of events in the Philippines and Argentina (or, for aught I know, in Bolivia or Brazil).

Which is not to say that provisional Carter-Reagan comparisons are idle. Panama without Carter's canal treaty would be a bleeding sore today; and without his good offices there probably would be no peace treaty between Egypt and Israel. Where, outside Ambassador Kirkpatrick's fancy, are Ronald Reagan's comparable achievements?