In 1976, Jimmy Carter almost lost the presidential election by losing lead of 30 points over Gerald Ford. So far, in the campaign of 1980, Carter has also lost 30 points to Ronald Reagan. In the latest polls, Regan is leading by 10 to 13 points instead of trailing by 20 points, as he was only a few months ago.

Since a lead of that magnitude would mean a decisive victory, if not a landslide, for the prospective Republican nominee, it is not surprising that the delegates to the GOP convention appear to be in a state of euphoria.

Delegates have been warned, however, by Sen. John Tower, chairman of the convention's platform committee, not to go overboard. "Republicans," he noted, "have a singular facility sometimes for snatching defeat from the jaws of victory. Disunity has cost us elections in the past."

Was Tower thinking back to 1964 when the party's right wing won control of convention, steam-rollered the opposition, nominated Sen. Barry Goldwater for president and rammed through an ultraconservative platform?

Then, as now, the dissidents, notably the out-numbered "Eastern Establishment" Republicans, were so powerless at the convention that there was no serious challenge to the right wing. Who will forget how Nelson Rockefeller, then the governor of New York, was booed and humiliated when he attempted to speak for the moderates.

In 1964, the convention, the nomination and the platform belonged to the right wing, but the election didn't. It was a pyrrhic victory for the extreme conservatives: the GOP moderates and independents defected en masse, and the upshot was a record defeat for Goldwater.

At Detroit, the Reagan forces, like Goldwater's troops, are in absolute control. There will be no Rockefeller to hoot at this time, but his protege, Henry Kissinger, is to be allowed a few grudging words. The former secretary of state has been advised that, if he wishes to avoid embarrassment, he had better not challenge the anti-detente, anti-SALT positions of Reagan and his followers.

The Reagan team argues that there won't be large disaffections this year because their man is not "another Goldwater," meaning he is not a "simplistic" hard-liner. That will be news to the Arizona senator, who in 1976 backed Ford for the GOP nomination because he thought Reagan was too extreme and jingoistic, particularly in opposing the Panama Canal treaty.

Goldwater feared Reagan's stand could lead to war over Panama, but the senator was shocked when former supporters bombarded him with abuse for criticizing Reagan. It prompted him to describe the right-wing faction in these terms:

"You'd have to know these people. They're wonderful, decent, kind people, but they just get carried away. They were the same ones who booed Rockefeller in 1964. They work their heads off, they get votes, they give money. But if they disagree with you one bit, you're a no-good SOB."

Things haven't changed much. In hammering out the party platform, the Reagan forces crushed all efforts to endorse the Equal Rights Amendment. Likewise, they beat down all opposition to the anti-abortion amendment, although they appear to be flouting public opinion on both these inflammatory issues.

The platform, as drafted, charges that U.S. defenses have been neglected and blames Carter for it. The drafters seem to have forgotten that Reagan, in campaigning for the nomination in 1976, put the blame on the Republican leadership then in power.

"Henry Kissinger's recent stewardship of U.S. foreign policy," Reagan said, "has coincided precisely with the loss of U.S. military supremacy . . . . Under Kissinger and Ford, this nation has become Number Two in military power in a world where it is dangerous -- if not fatal -- to be second best."

The notion that Reagan cannot match or surpass Goldwater in making campaign gaffes is hard to sustain. It wasn't the 1964 nominee who proposed blockading Cuba to force the Russians out of Afghanistan, nor was it the Arizona senator who both favored and opposed the Olympic boycott. It was Reagan who recently told America's farmers that he wasn't quite sure what "parity" meant.

Despite the platform fight, Tower foresees a united party in the fall campaign. Speaking of ERA, he found it "refreshing" that it "seems to be the only issue that divides Republicans . . . . Everybody acknowledges the unity of the party on everything else."

Everybody? Tower, a Texas, apparently is not very familiar with the moderate "Eastern Establishment" that is so despised by the ultraconservatives. Just in the last week, a number of the Establishment's wealthiest and most influential figures have started raising campaign funds for John Anderson.