The rage on the right over President Reagan's turn to diplomacy in Nicaragua may be a symptom of deeper disquiet among conservatives about the state of their movement. As the 1988 election approaches, we're hearing the kind of static in that sector of the political spectrum that usually comes from forces much farther to the left.
You had to be deaf to miss the howls of rage over Reagan's embrace of a ''peace plan'' advanced by House Speaker Jim Wright (D-Tex.). That plan was soon supplanted by a somewhat similar but squishier proposal from five Central American presidents, and the White House -- to the further dismay of conservatives -- called that a ''positive'' initiative as well.
''Fiasco,'' cried The Wall Street Journal in an editorial titled ''Reagan's Bay of Pigs.'' Columnist William Safire saw ''appeasement,'' and others on that side of the aisle claimed it was a sellout of the contras.
Republican presidential candidates joined the uproar, with Jack Kemp saying the administration apparently has ''no strategy to deal with the Soviet threat in Central America.'' Even loyal Vice President George Bush felt the need to assure a Miami audience that the United States would ''not leave the contras twisting in the wind, wondering whether they are going to be done in by a peace plan.''
Bob Dole and Pete du Pont voiced similar worries. All of them said they believed in the old Reagan of the ''freedom fighters'' and the Reagan Doctrine, not this newly minted substitute.
This is not just the political version of New Coke vs. Classic Coke. True, the electorate in the Republican primaries tends to be as far right of center as the Democratic primary voters are to the left. But something more than pandering has caused so many conservatives to bail out on Reagan on this issue.
It's a symptom of the decline of his moral authority, even within the Republican Party. Sure, any one of the GOP's 1988 hopefuls would like Reagan's endorsement (which he's not likely to give). But they also sense an erosion of his standing with the conservative activists and a need to tell those folks, who make up the most important constituency in today's Republican Party, that they are prepared to be more principled than the president.
Part of this is the legacy of selling arms to Iran. That act stripped Reagan of his reputation for consistency and moral rectitude. It clearly undercut his stated view that the United States should never traffic with terrorists. It left him vulnerable to being ''snookered'' by a bunch of folks who conservatives, even more than most other Americans, find obnoxious.
But the erosion of Reagan's moral authority has deeper roots. It goes back to his themeless 1984 re-election campaign and to the frequent signs of passivity in the face of provocations his fellow conservatives thought should have stirred him to anger and to action.
Disillusionment is the theme of a round table in the September issue of The American Spectator, a favorite magazine of the right, in which eight well-known conservative writers discourse on what Spectator Editor R. Emmett Tyrrell Jr. calls ''the coming conservative crack-up.'' They say hard things about the advertised ''Reagan revolution.''
In a typical lament, columnist and National Review editor Joseph Sobran writes: ''Reagan gave conservatism a beachhead in Washington, but he didn't follow through. For a few rounds he was dazzling; then, when he seemed about to score a knockout, he ran out of gas and spent the better part of a year trying to rope-a-dope his way through the Iran-contra mess.''
Tyrrell and several of the others put less blame on the man and more on the movement. Here's Tyrrell trashing his friends: ''The conservatives were not resourceful enough to insulate their President against dissolving into sentimental appeasement toward his Iranian foes. In six years of presidential power, the conservatives never significantly affected the climate of American ideas. . . . The conservatives have not adapted to an era that is moving beyond the problems of the early 1980s.''
It galls these writers that in a heavily delegated presidency, Reagan has chosen three successive chiefs of staff -- James Baker, Donald Regan and Howard Baker -- who have no roots in the conservative movement and no commitment to its future. It angers them even more that they are plagued by what Ernest van den Haag calls ''habitually cliquish and sectarian . . . divisiveness'' in their own ranks.
Some of this rhetoric is probably just the seventh-year itch. The realization is sinking in that Reagan is nearing the end of his second term and that most of his achievements are behind him. But it's more than that.
When Reagan muddies the message, as he did by selling arms to the ayatollah and now by seeming ready to subordinate the contras' cause to a negotiated settlement in Nicaragua, the morale of his most ardent supporters suffers.
It looks as if the first challenge facing Reagan's would-be Republican successor is to restore a sense of confidence and coherence to the conservative activists. And that may be tougher than anyone supposed